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atoms, which either saturate the electro-negative ele- Metals which are ordinarily quite strongly electroment or link hydrogen to it, as the case may be. Thus, positive may in the presence of a very strong base sulphur, an electro-negative element, forms a series of figure as electro-negative or acid-forming in the comacids according to the valence displayed by it in the binations with these strong bases. Thus, the evolution several cases, and according to the part the oxygen of of hydrogen from the action of zinc upon potassium the compound plays, whether simply linking or partly hydrate solution is explained on the assumption of the linking and partly saturating. We will give the form- formation of a potassium zincate or the solution of aluulas and the molecular structure of this set as illustra- minum hydrate in strong alkali by the formation of an tive of the class of acids referred to:

alkaline aluminate. The same metal is sometimes asHyposulphurous Acid (Hydro-sulphurous of Schütz- sumed to exist in both electro-positive and electroenberger),

negative conditions in one combination. Thus, red H2SO2 or H -()-S-0-H,

lead, which, when decomposed by nitric acid, yields lead in which the negative group is SO2, and the oxygen has nitrate and lead peroxide, is considered to be a plumbic only the linking function.

plumbate or compound of dyad lead as base and tetrad Sulphurous Acid,

lead as acid-forming element. A similar case is also H2SO3 or 0-S-O-H,

found in the case of antimony, which is generally elec

tro-negative, but forms a very stable compound Sb,0, in which the negative group is SO3, and the oxygen is ($b”Sb.), antimony antimonate, derivable from anpartly saturating and partly linking oxygen.

timonic acid H Sb0. Sulphuric Acid,

Organic acids, frequently very complex in formula, H2SO4 or -0-H

may still be brought under the simple definition of

acids given above. Indeed, the_definition may be in which the negative group is SO., and the oxygen is made still narrower in their case. They are compounds partly saturating and partly linking.

of electro-negative groups with replaceable hydrogen, Other common acids of this class are

or rather with hydroxyl, as oxygen always links the

hydrogen to the rest of the formula. They are made Hypochlorous acid, HCIO or Cl. — он, ,

more complex, however, by the fact that these electroChlorous HCIO, or CI''0 -OH,

negative groups contain the same elements, carbon, hyChloric

HC103 or CI 02 – OH,
HC104 or Clvi03 – OH,

drogen, and oxygen, as other groups acting electroNitrous HNO2 or N'''0 -OH,

positive, and are indeed formed from these latter by Nitric HNO3 or NPO2 – OH,

oxidation. So that an organic acid is distinguished Phosphoric

H3PO4 or PNO - (OH), by its containing an oxidized radical as distinguished Metaphosphoric HPO3 or P'02 -OH, from the alcohol or unoxidized radical, which acts

electro-positive or basic. Thụs, acetic acid C,H,O.OH Pyrophosphoric HP207 or POOH

is derived by oxidation from ethyl alcohol CH3OH 0

and benzoic acid C.H.CO.OH from benzyl alcohol PO OH

C6H3.CH,OH. The molecular structure of this oxiон,

dized radical may vary very greatly, but its hydrate Carbonic

H2CO3 or civo - (OH)2, will still be an acid. Indeed, we may have two acids Silicic

H2SiO3 or Siro - (OH)2. of the same ultimate formula, the sole difference beIn all these cases the hydrogen of the acid is con- dized radical are differently arranged in the two. Th

tween them being that the atoms constituting the oxinected to the electro-negative element by oxygen, constituting, with it the group hydroxyl. Upon the we have two varieties of lactic acid

C,H,O3, the molecnumber of hydrogen atoms so connected, or, in other ular formula of the one (the lactic acid" of fermenwords, the number of hydroxyl groups, depends the

CH, basicity of the acid. If hydrogen occur in the formula not replaceable by metal, we assume that it is not tation) being CH.OH,

CH.0 so connected. Such cases are common among organic acids when the hydrogen either belongs to the electro

CO.OH negative group itself or is attached to it as character

CH, OH istic of of compounds , and hence is called aldehydic hydrogen. Among inorganic while the other (sarco-lactic acid) is CH. acids we have two compounds that probably are of this latter character. They are hypophosphorous and phos

CO.OH phorous acids. In the case of these two acids the basicity of the acid does not agree with the pumber of been sometimes assumed to be characteristic of an

The presence of the group CO.OH (carboxyl) has hydrogen atoms they contain. Thus, hypophosphorous acid HỌPO, is only monobasic, and phosphorous acid organic acid, but it is now admitted that this is not H,PO, is dibasic. In explanation of this anomaly their essential

. Whether an organic hydrate is to act as structural formulas are written

alcoholic (or basic) or as acid, seems to depend simply on

whether the hydroxyl attaches itself to a carbon atom (H H

already linked to oxygen or not. The oxygen with the POH and POOH,

carbon atom and the hydroxyl may make the group OH OH

CO.OH, or it may be otherwise grouped. respectively, when the number of hydroxyl groups at (For the secondary characters of acids, and also the once shows the true basicity.

physical tests by which they are generally recognized, A third class of inorganic acids are those in which see original article on Acids.)

(S. P. s.), the characteristic or fundamental element is not always ACKNOWLEDGMENT, in law, the act of one who electro-negative, but in its union with oxygen forms has executed a deed in going before some competent groups either electro-negative or electro-positive, ac- officer designated by statute and declaring the same to cording to the valence displayed by it in the particu- be his act and deed. The term is also used to indicate lar case

. Thus, chromium may form electro-positive or the certificate appended by the officer to the deed, which base-forming groups in the case of its lower oxides, or sets out the manner and fact of the acknowledgment. an electro-negative group when occurring as chromium In England it is not the practice to acknowledge trioxide CFO3. Examples of this kind are the chromates, deeds ; in the United States the custom is universal

. which are the salts of chromic

acid H,Cro,; the manga- The functions of an acknowledgment are in the United nates

, derived from manganic acid H,Mn0,; the per- States twofold: (1) to authorize a deed to be offered in manganates, derived from permanganic acid 'HMnO,; evidence without further proof of its execution; (2) to the stannates, derived from stannic acid H,SnOz. enable it to be recorded.

The power to take acknowledgments is by law vested | at All Souls. In 1848 he took the degree of Christ in different persons in the various States. Generally, Church, having been previously appointed Lee's reader it may be said that any judge of the courts or court in anatomy. In 1849 he became physician to the Radofficer, mayor or other chief magistrate of a city, magis- cliffe Infirmary.. During this period, with the aid of trate, alderman, justice of the peace, or notary public several able assistants, particularly Profs. Beale and is authorized to take acknowledgments.

Melville and Mr. Charles Robertson, he made the valThe usual form of acknowledgment is for the person uable Christ Church physiological series, now in the executing the deed to appear before the appropriate Oxford University Museum. He became in 1858 Reofficer and to declare that the instrument is his act and gius professor of medicine, and in 1860 accompanied deed. In most of the States, however, the acknowledg- the prince of Wales to America as his medical attendment of a deed by a married woman is a somewhat ant. In 1866 he was appointed a member of Mr. Gamore elaborate ceremony. The woman is examined thorne Hardy's “cubic-space commission," and in 1869 separate and apart from her husband, and declares that of the royal sanitary commission. Since 1858 he has the deed is her own voluntary act, without any coercion acted as representative of the University of Oxford in or compulsion on her husband's part.

the medical council

, has been president of the British In order to entitle a deed to be put in evidence with Medical Association, and president of the physiological out further proof of its execution, or in order to enable section of the British Association. He published a it to be recorded, the certificate of acknowledgment treatise on The Plains of Troy in 1839, and a valuable must affirmatively show that all the requisites the Memoir on the Visitation of Cholera in Oxford in 1854. particular statutes in force in the State have been sub- In addition to these he is the author of numerous treastantially complied with.

tises on medical, sanitary, and scientific subjects. The term "acknowledgment” is also used in law to ACONITINE. Aconitine, as met with in pharmacy, indicate an admission, particularly an admission of a is of somewhat uncertain composition, the name having debt due, so clear, explicit, and unconditional as to re- been applied to an amorphous alkaloid, or at best to a move the bar of the statute of limitations. (L. L., JR.) mixture of amorphous and crystallizable bases, extract

ACLAND, LADY HARRIET (1750-1815), was á ed from Aconitum napellus and from mixtures of that daughter of the earl of Ilchester, and was born Jan. 3, and other species. 1750. Her maiden name was Christiana Henrietta According to Wright, who with several colaborers Caroline Fox Strangeways, but after her marriage in has worked for years upon these roots, 4. napellus Sept., 1770, to John Dyke Acland, eldest son of Sir contains a highly crystallizable alkaloid of the formula Thomas Acland of Devonshire, she was generally C33H43N012

, to which the name “aconitine" properly known as Lady Harriet Acland. Her husband was a belongs. It also contains in smaller amounts pseudmember of Parliament for Callington, Cornwall, and in aconitine, another active alkaloid which is crystalli1774, while still holding his seat in Parliament, entered zable, but yields mostly amorphous salts. Both the the army. Becoming major of the Twentieth Foot in aconitine and pseudaconitine are decomposed by the the next year, he was chosen by Gen. Burgoyne to ac- action of mineral acids, alkaline solutions, or simply company his expedition against the American colonies. by the action of water in sealed tubes, according to Reaching Canada in June, 1776, Major Acland left his the reactions, wife in Montreal, but she twice rejoined him in camp,

C33H43N012 + H2O=CH6O2 + C26H39N011. and nursed him till restored to health. Then, refusing

Aconine. to be separated from him, she accompanied the advance C36H49N011 + H2O C9H1004 + C2H41N08. of the army, though her husband's command was at

Dimethyl protocate- Pseudaconine. the front. At the second battle of Saratoga, Oct. 7, 1777, he was shot through both legs and taken pris

Both of these alkaloids, aconine and pseudaconine, oner. As soon as she heard of his capture she obtained are said to have been found free in the roots of aconia letter from Gen. Burgoyne, and, accompanied by tum. Some roots contain in addition a nearly inert, Rev. Edward Brudenel and a few others, sailed down bitter base termed picraconitine C3H4N010 and another the Hudson to the American lines. She was court- amorphous alkaloid. eously received, and a few days later Gen. Gates sent According to Wright and Luff, Aconitum feroc conher to Albany, whither her husband had been conveyed. tains chiefly pseudaconitine, with a little aconitine and When he recovered they visited New York and formed an amorphous alkaloid. According to the same auvery favorable impressions of the people. Major Ac- thorities, Japanese aconite contains a new base, Japland, being exchanged, returned to England, and in aconitine CHEN,0,1, which resembles aconitine very 1778 he fought a duel at Bampton Down with an closely, having the same fusing-point (185° C.), but officer who had aspersed the character of the Ameri- yielding different decomposition-products upon treat

At the time of the duel he caught a severe cold, ment with acids or alkalies. which terminated in a fever, and he died at Piston Aconitum heterophyllum, lastly, contains atisine, an Hall, Oct. 31, 1778. Lady Harriet never married amorphous alkaloid of intensely bitter taste. Broughagain, and through the rest of her life could not refer ton, its discoverer, assigns to it the formula C.H,N,05. to her husband without tears. In her youth she was The drug is devoid of acridity and does not contain noted for gracefulness and delicate beauty ; in later life aconitine.

(s. P, s.) she is said to have suffered from cancer, though she ACOUSTICS. To the statement of the principles concealed the fact till her death, which took place at

and facts of the science of ACOUSTICS, as Tetton, July 21, 1815. Her Letters and Journals, p. 93 Am. given in the Encyclopædia Britannica, the giving an account of her experiences in America, have ed (P. 100 following important details and new discovbeen published. For a long time her adventures fur- Edin, ed.). eries should be added : nished a favorite subject for pen and pencil, and several Atmospheric Influence. —Experiments in signalling romantic additions were made to her story without with sonorous instruments on the coast during fogs have foundation in fact. One of these was, that after the led to a preference for the siren over the trumpet, and death of Major Acland she was married to the chap- for the trumpet over the whistle. They have disproved lain who had escorted her from the British to the the notion that sounds travel farthest in fine weather. American army. (See articles by William L. Stone in On the contrary, sounds are heard at greater distances the Magazine of American History, iv. 449, and in Lip through fog, snow, hail, or rain. Perfect stillness pincott's Magazine, xxiv. 452.)

and uniform density and temperature are found to ACLAND, HENRY WENTWORTH, M. D., F.R. S., be most favorable conditions for the transmission D. C. L., fourth son of Sir Thomas Dyke Acland, Bart., of sound-waves. The velocity of sound (which is was born in 1815, and educated at Harrow and Christ seven hundred times greater than that of a breeze) is Church, Oxford. In 1841 he was elected to a fellowship not sensibly affected by the wind. It is sometimes


Benzoic acid.


chuic acid.


See Vol. I.

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conveyed better against the wind or at right angles | may receive some confirmation. At Maidenhead railwith it than when both proceed in the same direction. way-bridge, however, the sounds are said to be grad

Sound travelling with the wind is refracted to the ually raised, and the echoes repeat the letter s more earth, and travelling against it is elevated several distinctly than is usually the case. hundred feet. Sound so lost may be heard again far Velocity of Sound in Different Media.-The velocity off

, being returned to earth by a contrary current, or of sound through metals at 20° C. or 68° Fahr. is as (from the spreading of the tone) it may arrive from follows: another point. Sounds unheard on the deck of a


4,030 feet per second. vessel may be clearly distinguished on the masthead.


5,717 This spreading of the tone in all directions on the ho- Silver

8,553 rizon is so marked a peculiarity that a fog-trumpet is Copper..

..11,666 heard nearly as well at equal distance behind as in

Platinum .........

8,815 front. Concave reflectors therefore are of little service.


.16,822 During early experiments the most conflicting results

Iron wire (ordinary) .16,130
Cast steel...

.16,357 were frequently obtained and generally accepted the

Steel wire (English)..

..15,470 ories disproved. Prof. Tyndall, on finding the sound obstructed in clear weather, assumed that streams of As a rule, these speeds are diminished by augmented air differently heated or saturated in different degrees temperature. Iron, within certain limits, is an excepwith aqueous vapors rendered the atmosphere floccu- tion. At 100° C. it reaches 17,386 ; at 200° C. it falls lent to sound; that invisible acoustic clouds incessantly to 15,483. The double echoes in coal-mines are due to passed through the air, intercepting the sound, wasting varying velocities. The velocity of sound in coal is it by innumerable reflections, as light is wasted in an estimated at 7000 feet per second. The sound of each ordinary cloud; and therefore that days of extraordi- stroke of the miner being transmitted through the coal, nary acoustical transparency may be followed by days and also much more slowly through the air, has given of extraordinary acoustical opacity. Archibald Forbes, rise to the story of his ever-heard but never-seen colain My Experiences of the War between France and Ger- borer. many (vol. ii. pp. 285–289), noted that the cannonad- Sound in Buildings. - Annoying echoes in buildings ing in the distance, which was well heard on cold, damp, may be modified by the hanging of curtains or the use of and foggy days, in extremely fine weather was unheard. matting to absorb the tone at those points from which it Such stillness reigned that it was generally believed the is reflected. The new cathedral of St. Finn Bar at Cork firing had ceased.

in Ireland, the nave of which is of great height in proProf. Henry, who for many years experimented on portion to the width, had a troublesome echo. Several fog-signalling, and gave us the best fog-signals in the thin wires, barely visible from below, were stretched world, recorded his doubt of the above conclusions that across the building, at certain points, and proved to be the screening effects were due to abnormal conditions, perfectly successful in destroying the echoes. They and believed that sound will pass through these "re- are now commonly used for this purpose, for the expergions of silence" freely enough in an opposite direction. iment is easily made, and the number of wires may be

As his experiences from 1865 to 1877 were not given readily increased until the adjustments are satisfactory. to the world, but recorded in purely official documents

, At the new cathedral of St. Patrick in New York it may be well to state that in the appendix to the re- six wires, near the west gallery, are sufficient. In port of the Lighthouse Board for the fiscal year end buildings intended for music the ceiling should not ing June 30, 1874 (p. 116), he says that a flocculent meet the wall at right angles, and other means should condition of the atmosphere, due to the varying den- be taken to prevent sudden checks to the progress of sity produced by the mingling of invisible aqueous the sound-waves and the consequent rebounding. Nor vapor, is a true cause of obstruction in the trans- should the ceiling be perfectly flat; it should have the form mission of sound-a fact borne out by the principles of the inverted hull of a ship or the roof of the mouth, of wave-motion as well as by experiment—but that he which is a resonant air-cavity. A certain amount of is far from thinking this to be the efficient cause of the resonance being desirable, although echoes are distressphenomena under consideration. That a flocculent ing to both musicians and orators, it is well to arrange condition of the atmosphere should slightly obstruct to have it in excess when the hall is empty, for the the sound is therefore not difficult to conceive, but dresses of the audience absorb very much tone. The that it should obstruct the sound-ray in one direction erection of a gallery across the hall opposite the stage and not in an opposite, or in a greater degree in one will sometimes destroy an echo, or a speaker by directdirection than in another, the stratum of air being the ing his voice under such a gallery may evade it. Wellsame in all cases, is not credible.

practised speakers and singers learn to adapt themselves Aërial Echoes. - It is believed by some that the strong to rooms by so directing their voices to particular points. and prolonged aërial echoes are produced in the clearest Speakers who are free to use whatever tones they choose air by acoustic clouds; and it is maintained by others sometimes adapt the pitch of their voices to the various that such echoes have been clearly heard when there halls in which they speak. A clergyman accustomed was no acoustic cloud in the direction of the prolongation to his own church preaches therein with less effort of the axis of the fog-trumpet; that these echoes have than in a strange building. been heard in all weathers and under widely differ- Although much stress is laid upon the advisability ing circumstances; that they become fainter, and not of having music-rooms planned in accordance with stronger, when approached, although they are more particular proportions as regards length, breadth, and continuous, increasing from five to twenty minutes; height, so that all the dimensions may be multiples of and that these, in common with many other phe- some unit of length, yet it appears that the influence nomena said to have been observed, await fuller inves- of a building in deadening or reinforcing and enhancing tigation.

tones depends as much upon the materials used as upon The atmosphere evidently exercises a selective choice the form adopted. Choir-singers attached to various upon the waves of sound continuously, sometimes favor- cathedral establishments in England have frequently ing tones of deep pitch and sometimes those of greater noticed the good effect of music sung in almost any old altitude.

building in the precincts, whatever its proportions. It Harmonic Echoes. - It may be an explanation of har- seems to have escaped observation that in all such cases monic echoes that the fundamental tones are weakened the buildings are of solid stone or good brick with moror lost, while the overtones are heard in full strength or tar so well made as to be stronger than the bricks themreinforced. When the original sound is required to be selves, and the wood is extremely hard and close-grained. of a character that is known to be rich in such overtones, In a diving-bell sounds are very loud, on account of and the intervening space is a wooded valley, this view the compression of the air. The intensity of sound depends on the density of the air where it is produced, ticularly sensitive to other vowels than a and u. The and not on that where it is heard, unless the latter air- roaring is attributed to the greater proportion of air volume be the denser. A partly deaf person will hear that mixes with the gas before it passes the gauze. better in a gallery than on the ground floor, whether It is then an explosive mixture that burns. It is the speaker be elevated or not.

hardly safe to excite flames within safety-lamps in Sound Compared with Light and Water. There mines. A flame produced by coal gas in a holder are analogies between the laws that govern the prog- under a pressure of ten inches of water, and issuing ress of sound, light, and water. Sound in its uni- from a steatite jet having a circular orifice 004 inch in formity of speed and in its decay by radiation resem- diameter yields a flame that is sensitive to vibrations bles light, but in its mode of deflection, reflection, and beyond the limit of hearing. By continuously raising absorption it partly resembles light and partly water. the pitch of a Galton whistle, the flame becomes more Sound, like water, can be conducted through tubes, and more agitated on passing the point of audibility; etc., as light cannot. Light travels in straight lines at every puff of the whistle the flame falls from 24 from its source, and consists of distinct impulses suc- inches to 8, roars, loses its luminosity, and when viewed ceeding one another and forming waves. In this it by a moving mirror presents a multitude of ragged. resembles sound. Waves of water, when they strike images, indicating a state of rapid, complex, and vigorat a more acute angle than 45°, are not perfectly re- ous vibration. This effect is produced when a distance flected. When they strike at a more acute angle than of fifty feet divides the sound and the flame. 30°, they seem to travel along the bank or other sur- Beats.-Players on stringed instruments and tuners face against which they have struck. Waves of sound, of pianofortes have noted the phenomen

nenon of beats however, are not only reflected, but also radiated, and from single strings. That these are not caused by often reinforced, by the sympathetic vibrations of bodies defects in the strings is sufficiently well proved. The which they strike while being transmitted.

beats are caused by some unknown peculiarity in the The mathematical theory of undulations shows that structure of the instrument, such as the shape and the waves of sound bend around obstacles, and produce position of the f holes in a violin with reference to the more or less effect within the geometrical shadow, while grain of the wood of the belly, want of correlation, etc. light-shadows are more sharply defined. This may This is called the "wolf," and generally occurs on D result from their difference of pitch, since we find that or F of the violoncello. Many mysterious phenomena the acoustic shadows cast by notes high in pitch are are peculiar to pianofortes. more distinct than those cast by deep tones. Sound There are three other kinds of beats-viz., those obresembles light also in a property like translucency, tained from unisons, from other concords (such as fifth, since some bodies give passage to only a portion of the third, etc.), and those formed by harmonics which are sound-waves.

perfectly in tune clashing with tempered intervals. The Polarization of Sound.-Prof. S. W. Robinson Approach Caused by Vibration.- Prof. Guthrieof the Ohio State University, having examined the na- Challis and Prof. J. Clerk Maxwell have experiture of vibrations in extended media, asserts that if they mented to determine the cause and conditions of the are produced from the action of a remote single centre of observed fact, that when a vibrating tuning-fork or disturbance, they can only be longitudinal, even in light; vibrating, disc is held near a piece of suspended that vibrations will be to some extent transversal when cardboard the latter has a tendency to approach the due to two or more centres of disturbance not in the fork or disc. This is not due to the establishment same line, as when two or more independent co-exist- of permanent air-currents. The approach begins from ent systems of undulations combine into one, or when distances far exceeding the range of Faraday's surface a simple system is modified by such lateral disturbance whirlwinds. The vibrating fork displaces air. The as a reflection or a refraction; that undulations to effect of apparent attraction is caused by atmospheric be in a condition called polarized probably consist of pressure which is due to pendulatory dispersion. The vibrations which are transversal, and that no necessity pressure of the air on the suspended body is less on the exists for assuming vibrations to be transversal in front side nearest the fork than on the opposite side. of a polarizer. His method of experiment is ingenious, Mercadier's Music Register.-A wire suspended by and the results are very interesting, but further experi- narrow strips of caoutchouc is soldered at one end to ments are necessary before a satisfactory knowledge of a small plate of brass which is placed between the the matter can be gained. Prof. Robinson, however, be- sounding-board of a violin or other stringed instrument lieves that the longitudinal character of the vibrations and the foot of the bridge. The other end is fixed to of sound has been proved by the repeated reflections he a heavy stand in such a manner as to communicate its gained from the surfaces of membranes separating coal vibrations to a feather which is also fixed to the stand. gas and air. A diminution in intensity was produced in this way the vibrations are of greater amplitude according to the relative positions of the membranes, than they would be if the feather were attached analogous to reflections of light from a series of glass directly to the wire. The feather is so placed as to plates. When the membranes used become, from record its motions on a smoked cylinder which may be any cause, too slack or too tense, the results are dis- turned by the hand. A tuning-fork is made to record appointing. Their tension must be carefully adjusted. its vibrations simultaneously on the cylinder as a chro

The Note of a Building.--It frequently happens that nograph, so that the cylinder need not be turned with an organ carefully regulated in every particular in the a uniform motion. The resulting wave-marks may be factory, and designed to fill with tone a given number of measured with the aid of a micrometer. cubic feet in a church of which the materials and shape Stereoscopic slides have been employed by Preece are known, on being erected in the edifice has one and Stroh to throw into perspective the very compliparticular note reinforced in a remarkable degree, so cated vibration-curves of sonorous bodies. that it seems almost impossible to reduce its power Miniature Whirlwinds.- If some lycopodium or other that it may be uniform in strength with others. This impalpable powder (such as that found in puff-balls or note is possibly one whose sound-wave is correlated to any fungus yielding very fine brown dust) be sprinkled the unit of measurement of the building.

with sand on a vibrating plate, it will collect at the very Sensitive Flames. The most sensitive flame is a con- poirets that the sand avoids. Were the experiment ical one having a deep blue base and yellowish apex, ob- performed in vacuo, the powder would mix with the tained from ordinary gas-jets by placing a wire gauze sand, for it is the upward and downward movement of (having 32 meshes to the lineal inch) about two inches the air in obedience to the vibratory action that causes above a Sugg's steatite pin-hole burner and lighting the the dust to dance over those portions of the plate where gas above the gauze. At the least noise the flame roars the action is greatest, and eventually to subside in heaps and sinks so as to become almost invisible. It dances away from the nodal lines. well to an ordinary musical snuff-box, but is not par- Recent Researches.--During the past ten years the


He was

science of acoustics has made very great advances. It! When a beam of sunlight falls upon lampblack, the has been demonstrated that the pitch of sounds is raised particles, being thus heated, expand, and cause a conif the vibrating body is approaching the hearer, and vice traction of the air-spaces or pores among them. When versâ. This is the basis of Prof. Doppler's theory of the light is cut off, the converse process takes place. the colored stars. Prof. Mayer raised a fork a minor The action is somewhat like that of repeatedly filling a third by rapid rotation. A jet of water descending sponge with water and squeezing it. from a circular orifice is found to consist of a succession Prof. Graham Bell made successful experiments of drops which may be analyzed by the electric spark, with solids, liquids, and gaseous matter, the sounds and like flames be caused to emit a musical sound and produced being sometimes audible all round a large respond to extraneous sounds.

He found that the vapors of the following The resonator of Helmholtz has aided materially in substances were highly sonorous in the intermittent many forms of research. In value and use it is analo- beam: water vapor, coal gas, sulphuric ether, ammonia, gous to the microscope. The invention of the mega- amylene, ethyl bromide, diethylamene, mercury; and phone, microphone, topophone, and harmonic telegraph that the loudest sounds were obtained from iodine and of Elisha Gray, the translating phonograph, the elec- peroxide of nitrogen. tro-motograph, musical telephone, and the singing and The names "thermophone," "photophone," and speaking telephone by Edison, and the general use of actinophone” are applied to instruments for the protelephones of varied forms and powers, form important duction of sound by thermal, luminous, or actinic rays steps of progress in applied acoustics.

respectively. "Radiophone" signifies an apparatus inActual Vibration Numbers. — The four methods of tended for utilizing any form of radiant energy. When finding the actual vibration numbers of notes described the color of the light is changed the sonority is also by Dr. Robert Smith of Cambridge University in his changed; thus, hard-rubber shavings, which will sing elaborate treatise on Harmonics (London, 1759), and in red, orange, yellow, and green, refuse to sing at all the formula given by Woolhouse in his work on musi- in blue, indigo, or violet. Green silk will sing in red, cal intervals, are now superseded. They were set aside but not in indigo. Coal gaš, in common with iodine on account of their liability to errors which could not be vapors, sings very lustily; hence the presence of fire. easily eliminated. The siren of Dove, though valuable damp may be thus detected.

(s. A. P.). to acousticians for general use, is not sufficiently accu- ACRELIUS, ISRAEL (1714–1800), a Swedish clergyrate or delicate for particular purposes.

man, author of a history of New Sweden, was born at When great exactness is required, the new chrono- Osteraker, Dec. 25, 1714. He graduated at the Uniscope of Schultz is employed. It consists of a metallic versity of Upsal, and was ordained in 1743. cylinder blackened by smoke, which is made to revolve appointed by the consistory of Upsal to the pastorate so close to a point attached to one of the prongs of a of the Swedish church at Christina (Wilmington), and tuning-fork that the vibratory motions of the latter may commissioned with the general charge of the Swedish be traced upon it. The cylinder is made to revolve by churches on the Delaware as their provost in June, machinery at uniform speed, although alterations in the 1749. He arduously devoted himself to his task, imrate of revolution would not vitiate the result. The proved the condition of his parish, attended to the afonly difference caused by such variations would be fairs of the other Swedish churches, preached in Swedish shown in the amount of space occupied by the curves and English, and collected much information on the state representing each vibration, and not the number of of the Lutheran churches in America. At a conferthese recorded in the given time. This chronoscope is ence of ministers at New Providence in 1753 he read a used during artillery practice at West Point. The fork Latin essay On the Origin and Progress of the Gerbeing regularly excited, the pendulum of a clock is ar- man Evangelical Congregations in Pennsylvania and ranged so as to touch a spring and thus send an electric the Adjacent Countries, which was printed in the spark to the recording cylinder. By this device the twentieth volume of the Acta Historico-Ecclesiastica. vibrations that have been recorded in a given space of At his request he was relieved of his charge in time are marked off. The interval during which a can- America in 1756, and appointed to the pastorate of non-ball passes through two targets is similarly marked Fellingsbro in the diocese of Westerås in Sweden. He off by sparks, and the vibrations are counted afterwards died at Fellingsbro, April 25, 1800. After his return in like manner. There generally remains a fraction of to his native land he wrote the work that has given a vibration. By the aid of a micrometer this fraction him a prominent place among the early writers on is accurately measured on the cylinder, for each vibra- colonial history, Beskrifning Om De Swenska tion may be, in the first place, divided into twenty Församlingars | Forna och Narwarande | Tilstånd, parts, and each of these parts again into one hundred | Uti | Det kallade Nya Swerige, ! Sedan | Nya Neparts. By thus subdividing one complete cycle or vibra- derland, | Men nu för tiden | Pensylvanien, samt nästtion of a tuning-fork making 250 vibrations per second, liggunde Orter wid Älf-wen De la Ware, Wäst- Persey calculations may be conveniently made in terms as small och News | Castle County uti Norra America. (Deas the five-hundred-thousandth part of a second. It is scription of the Former and Present Condition of the easy to see that by employing a fork of higher pitch Swedish Churches in what was called New Sweden, (say, B natural, the middle line of the treble staff, with afterwards New Netherland, but at the Present Time 500 vibrations per second) this interval of time could Pennsylvania, Stockholm, 1759.) The book does not be as easily subdivided into one million parts. . In con- confine itself, as might be inferred from its title, to sequence of Prof. Mayer's discovery that a variation of ecclesiastical matters, but contains interesting chapters 1°Fahr. caused a difference of ‘0125 in a fork produc- on the political history and social state of Pennsylvania ing 256 vibrations per second, and a difference of 023 in and New Jersey, and is considered a valuable source another making 512 vibrations, and other slight varia- of authentic information. A portion of it was transtions, the fork is now frequently tested, and elaborate lated into English by Rev. Dr. Collin, the last Swedish contrivances are devised to prevent the slightest inac- rector of the churches on the Delaware, and was curacy.

printed in the Collections of the New York Historical Sound from Radiant Energy. The photophone is Society in 1841. The desire for an English translation an instrument for the production of sound, even from of the whole work was at last gratified in 1874. The non-conductors of sound, by the action of an intermit- translation, made by Rev. Wm. M. Reynolds, was pubtent beam of white light. It is thus proved that sono- lished under the joint auspices of the historical societies rousness is a property of all matter. The loudest sounds of Pennsylvania and Delaware, and forms the eleventh are produced from substances in a loose, porous, spongy volume of the Memoirs of the Historical Society of condition, such as cotton wool, worsted, fibrous mate- Pennsylvania. rials generally, cork, sponge, etc., and also from those ACROMYODI (Gr. åkoos, pointed; pūs, muscle), in that have the darkest or most absorbent colors. ornithology, one of the primary divisions of the great

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