Imágenes de páginas
PDF
EPUB

of air an hour to a horse, with a velocity of 28 inches a second, which may be produced by a difference of temperature of 11° to 130 between the external air and that of the stable. This requires that the chimneys have a sectional area of 108 to 124 square inches to a horse.

By means of this ventilation, the hygrometrical condition of the air in the stable will be maintained within convenient limits.

144. Use of gas-burners.—The ventilation of stables may be increased by making use of the heat given out by gas-burners used to light them up at night, which then allows of reducing the sectional area of the ventilating-pipes.

145. Cow-houses.— Wbat precedes relates to work.animals. In the case of milch-cows, it appears that a certain drowsy laziness is favora ble to the production of milk; and in such cases it is necessary to limit the ventilation to what is absolutely necessary for health.

MEANS OF CONTROL.

146. Means to be used to determine the condition and the results of a system of ventilation. It has been shown by the numerous examples that precede that the establishment of a complete and regular renewal of air in occupied places in reality presents no difficulty, and that the rules to be followed are very simple. Their application will be equally so, and will involve but little expense if architects take care to devise plans of ventilation at the same time that they make the plans for construction, instead of waiting till the building is almost finished.

But when all the arrangements have been made to secure the renewal of air, the first thing to do is to examine whether the desired results have been obtained, and the second is to regulate the operation of the apparatus.

To determine what are the amounts of air carried off and drawn in, a small portable instrument is used, called an anemometer, consisting of a wind-mill with light and easily moved vanes, connected with gearwheels and pointers, which indicate the number of turns made by the vanes in a given time.

Experiments show that with an apparatus of this kind the velocity of the air may be deduced from the number of turns of the wings by means of an equation of the form :

V = a + b N V being the velocity in a second; a, a coustaut term, expressing the velocity of the air at which the in

strument commences to move; b, a constant number; N, the number of turns indicated in a second. Thus, one of the anemometers of the Conservatory has the formula:

V (in inches) = 8.66 + 7 N This instrument should be placed, as far as possible, in a part of the fue traversed by the air, where the velocity is uniform and well regu

lated. It should be kept in operation at least two minutes, if a watch indicating seconds be used ; and four or five, if a watch indicating minutes only is employed. From the number of turns made in this interval of time may be deduced that corresponding to a second, whence the velocity, V, may be obtained. This velocity, multiplied by the sectional area of the flue, will give the amount of air passing through in a second, and from this the amount passing through in 3,600 seconds, or an hour, can be obtained.

If it be feared that the velocity in the flue is variable, on account of its large size or other circumstances, it will be necessary to try the instrument at different places, which will then give with sufficient exactness the mean velocity of the air.

When it is desired to determine the volume of air which is carried out or drawn in through an opening covered with a grating, the anemometer should not be placed above or in front of this opening, as is done by many observers, and the velocity resulting from the number of turns observed taken as the mean velocity of the air passing through. Serious errors will result from this method. The proper way is to place before the opening, and fitting to it as closely as possible, a pipe having at one end the form of the opening, and joining at the other end a cylindrical pipe at least 2 feet long, in which the anemometer should be placed, which would then indicate the velocity of passage in this part of the auxiliary pipe. The velocity of the air introduced or withdrawn in a second or an hour may easily be deduced afterward.

147. Means of insuring the regularity of the ventilation.-While the use of portable anemometers serves for experimental investigations and for the determination of the results obtained by the ventilation, it is not sufficient to secure the necessary regularity of ventilation in large establislıments.

In such cases it is necessary to introduce much larger anemometers, connected with an electrical recording-apparatus placed in the office of the superintendent, or in a conspicuous place where it can be seen every hour, or every morning and evening, wbether the renewal of air is pro. ceeding with regularity and with the prescribed energy.

This is not the place to describe the apparatus.* I confine myself to stating that an anemometer of the kind has been employed with success for several years at the Conservatory of Arts and Trades, to insure regularity in the ventilation of the lecture-rooms; and that every year it works for about five consecutive months without derangement, and without requiring any care but the renewal of the solutions in the battery two or tbree times a season.

A similar anemometer has been in constant operation for several months in the ventilating.chimney at Lariboisière Hospital, and has serred to show, every morning, the annount of foul air removed from a

* See the Annales du Conservatoire, vol. 5, 1864, p. 341.

wing containing 106 beds, during the night, and, every evening, the amount during the day.

Methods of observation of this kind, automatic and independent of the personal action of the employés, are the indispensable adjuncts of great ventilating systems, if it be desired that the service be performed in a regular manner. They also serve to render the work of inspection by the heads of the establishment more easy and efficient.

Errata in previous portion of this article contained in the report for 1873:

In Ø 31, pp. 308, 309, for 1,000 cubic feet weigh, read one cubic foot weighs ; and for ucight of 1,000 cubic feet, read weight of one cubic foot.

In 0 35, pp. 310, 311, for 0.0000756, 0.000081, 0.000005, 0.000077, 0.000074, 0.000003, read 0.0756, 0.081, 0.005, 0.077, 0.074, 0.003 respectively,

ETHNOLOGY.

[It is considered important to collect all possible information as to the location and character of ancient earth-works, which exist in various parts of the United States, with a view to classify them and determine their distribution in relation to special topographical features of the country as well as to different regions. For this purpose the correspond. ents of the Institution are respectfully requested to furnish information as to any ancient remains of this character existing in their neighborhoods.-J. H.]

ANCIENT GRAVES AND SHELL-HEAPS OF CALIFORNIA.

BY PAUL SCHUMACHER.

During my visit to that part of the California coast between Point San Luis and Point Sal, (Map A,) in the months of April, May, and June, of 1874, I often bad occasion to observe extensive shell-heaps, like those I had found about a year previously so numerous along the shores of Oregon. These deposits of shells and bones are the kitchen refuse of the earlier inhabitants of the coast regions, where they are now found, and, though differing from each other in their respective species of shells and bones of vertebrates, according to the localities and the ages to which they belong, they have still, together with the stone implements found in them, a remarkable similarity in all parts of the North American Pacific coast that I have explored-a similarity that extends further to the shell-heaps or “ Kjökken-möddings" of distant Denmark, as investigated and described by European scientists.

In Oregon, from Chetko to Rogue River,* I found that these deposits contained the following species of shells: Mytilus Californianus, Tapes staminea, Cardium Nuttallii, Purpura lactuca, &c.; eight-tenths of the whole being of the species first mentioned.

In California, on the extensive downs between the Arroyo Grande and the Rio de la Santa Maria, the mouth of which latter is a few miles north of Point Sal, I found that the shells, on what appear to have been temporary camping-places, consist nearly altogether of small specimens of the family Lucina; so much so that not only can scarcely any other sort

• Of the collections made by the writer at that place, the complete and illustrated description will be found in the Smithsonian Report for the year 1873, p. 354.

[ocr errors][ocr errors][ocr errors][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][ocr errors][ocr errors][merged small][ocr errors][ocr errors][merged small][ocr errors][ocr errors][merged small][ocr errors][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][ocr errors][merged small][ocr errors][ocr errors][merged small][ocr errors][merged small][ocr errors][ocr errors][ocr errors][merged small][merged small][ocr errors][merged small]
« AnteriorContinuar »