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Notwithstanding what is affirmed in the page of our Review above referred to, it does not appear that the Author has succeeded in diffolving gold, while in its metallic ftate, with this acid fingly. He might possibly be deceived by the golden colour which this acid aflumes, even when alone, after about one half of it has been drawn off in distillation. He succeeded however in dissolving a calx of that meal.

Employing a precipitate of gold made by Cult of tartar, and digesting eight grains of it, during a month, with half an ounce of the animal acid; it was evident that, though a considerable part of the calx remained at the bottom of the vellel, a sensible part of it had been dissolved : for, on adding to the clear fluid a little of the volatile tincture of sulphur, a portion of gold fell down, in the form of a darkith yellow precipitate. A part of the same clear folution, likewise, being evaporated, exhibited irregular yellow cryftals.

On the addition of a small portion of nitrous acid to the animal acid, the Author procured a solution of gold, in its metallic ftate. When to 80 drops of animal acid he added only 20 of spirit of nitre, he observed evident signs of a gentle solution. On adding 20 drops more of the nitrous acid, and employing heat, a leaf of gold was totally diffolved. This experiment, says the Author, evinces a notable difference between the new acid, and that of falt: for it is evident that gold cannot be dissolved by a mixture of two parts of smoking marine acid, and one of aqua fortis.

The Author proceeds to relate the results of various experiments made with this acid, and the different metals and semimetals, as well as several neutral salts: but for his account of these numerous trials, we must refer our chemical Readers to the Article itself. Article 1. Relazione di una nuovo, &c. Aicount of a new kind of

Rain. Written by the Count de Gisini, an inhabitant of the 3d Region of Mount Etna, &c.

This article contains the chemical analysis of a coloured cretaceous grey water,' which fell in a shower of rain, that extended over the fields, about 70 miles, in a right line from the top of Ætna. On evaporating a portion of it, and touching is (to use the language of the Translator) with vegetable alcaline liquors (folutions of fixed vegetable alcali] and mineral acids; a Night effervescence was occafioned by the latter. Syrup of vio lets being added to it, had its colour changed to a pale green. Hence the noble Author was persuaded that it contained what he calls a' calcareous falt. By this term we afterwards learn, that he means 'a marine salt combined with a calcareous subItance' by a violent heat. We luppose the Author understands, marine acid combined with calcareous earth. The earth left on the total evaporation of the water, being calcined, was found to contain iron in a metallic state. On the whole for our noble observer does not appear to be a profound chemiftwe may infer, that the solid contents of the rain in question were the effects of a volcanic cruption. Article 6. An Account of some Scoria from Iron Works, which re

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femble the vitrified Filaments described by Sir William Hamilton : By Samuel More, Esq.

In the 70th volume of the Philosophical Transactions, Sir William Hamilton, treating of an eruption of Mount Vesuvius, gives an account of certain long filaments of vitrified matter, like spun glass, which were mixed with and fell with the ashes, The origin and nature of these curious filaments are explained by the Author of this Article; who has presented the Society with a specimen of some fag, or vitrified cinder, taken from one of the largest works in England for smelting iron; and which, by means of the strong blaft of air from the bellows, has been drawn out, while in its fluid state, into cobweb-like threads (some of them 10 or 12 feet in length) which being driven upwards by the blast, fix themselves to the beams and · other parts of the bellows room. They are so extremely ílender, as to resemble cotton in appearance; but, being examined with a microscope, are found in all respects similar to those described by Sir William Hamilton; which are undoubtedly formed of the melted lava, ejected from the mouth of the crater, and probably drawn out into threads, by the force of those violenc torrents of air which must be required to support so intense a body of fire as that of the volcano.

ELECTRICITY. Article 16. Del modo di render, &c. Of the Method of rendering

very sensible the weakest natural or artificial Elettricity: By M. Alexander Volta, Professor of Experimental Philosophy in Como, &c. &c.

There are few philosophers who have contributed more largely to the improvement of electricity, and indeed of some other branches of philosophical knowledge, than the very ingenious Author of this Article; who here gives us some electrical observations of a curious and fingular nature : particularly the description of a simple apparatus, by means of which, the smalleit, and otherwise impercepcible, degrees either of natural or artificial electricity are rendered senlible. What the microscope effects, in bringing to our view bodies otherwise to. tally invisible, is performed by this electrical magnifier, with respect to electricity ; by its rendering sensible such small quantities of that fluid, as would otherwise wholly escape the notice of our senses. Nor is this a mere marier of barren curiosity only; but may-it will soon appear that it has already- let us inio some of the secrets of nature's operations, particularly reIpecting meteorology.

The apparatus, by which these effects are produced, is no other than the Author's well-known Electrophorus; the refinous coat of which ought to be exceedingly thin (not perhaps above the 50th part of an inch in thickness); and its surface, as well as that of the metal plate adapted to it, should be as plain and as smooth as poffible.

When the sky is perfe&ly clear, and free from electrical clouds, so that an insulated conductor, fitted up to observe the electririty of the atmosphere, does not exhibit the least sign of electricity, by even attracting the finest thread ; if a temporary metallic communication be made by means of a wire between the atmospherical conductor and the metal plate, lying on the refinous surface; and this communication be suffered to fubfift for a certain time: on removing the wire, the metal plate will, on being lifted up, exhibit evident figns of electricity, by attracting light bodies, and giving sparks. In this case it is sometimes found neceflary to prelerve the communication of the eleElrophorus with the atmospherical conductor even 8 or 10 minutes. But if the atmospherical conductor alone be capable of barely attracting a light thread; the communication above mentioned need to last a few seconds only: in which time the metal plate will receive, and, as it were, condense such a quantity of electricity, as to dart even a strong spark.

The effects produced by this apparatus appear as extraordinary in discovering the presence of artificial electricity, when it is so weak as to be scarce or at all perceptible by any other means These appearances too are connected with a hitherto unobserved property of what may be deemed a new class of bodies, such as marble, dry wood, &c. and which may be called femi-conductors, or half-conductors. In this case, the refinous place is not wanted :- but the relation of one experiment will best explain our meaning.

Let a Leyden vial be charged, and then discharged; fo that it will scarce affect a light thread : or—as we have varied the experiment, in order to obviate cerrain objections-let an uncharged Leyden vial be brought to the conductor of an electric cal machine; so as to receive from it only two or three moderate fparks. If the metal plate only of the electrophorus (or condenser) be placed on a dry marble Nab, a table, or dry piece of wood, or any other imperfe&tly conducting substance, and the knob of the vial be made to touch the metal plate, or, in some cases, to pass over its surface; the latter, on being lifted up, by its infulating handle, will be found to be highly ele&trified, so as to give very Itrong sparks : and this it will do repeatedly for some time, on alternately applying the knob of the vial to the metal plate, and then lifting up the latter from the flab, and examining it,

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found to contain iron in a metallic state. On the whole for
our noble observer does not appear to be a profound chemill-
we may infer, that the solid contents of the rain in question
were the effects of a volcanic eruption.
Article 6. An Account of some Scoria from Iron Works, which re-

femble the vitrified Filaments described by Sir William Hamilton :
By Samuel More, Esq.

In the 70th volume of the Philosophical Transactions, Sir William Hamilton, treating of an eruption of Mount Vesuvius, gives an account of certain long filaments of vitrified matter, like spun glass, which were mixed with and fell with the ashes, The origin and nature of these curious filaments are explained by the Author of this Article; who has presented the Society with a specimen of some fag, or vitrified cinder, taken from one of the largest works in England for smelting iron; and which, by means of the strong blaft of air from the bellows, has been drawn out, while in its fluid state, into cobweb-like threads (some of them 10 or 12 feet in length) which being driven upwards by the blast, fix themselves to the beams and other parts of the bellows room. They are so extremely ilender, as to resemble cotton in appearance; but, being examined with a microfcope, are found in all respects similar to those described by Sir William Hamilton; which are undoubtedly formed of the melted lava, ejected from the mouth of the crater, and probably drawn out into threads, by the force of those violent torrents of air which must be required to support fo intense a body of fire as that of the volcano.

ELECTRICITY.
Article 16. Del modo di render, &c. Of the Method of rendering

very sensible the weakest natural or artificial Electricity : By M.
Alexander Volta, Professor of Experimental Philosophy in
Como, &c. &c.

There are few philosophers who have contributed more largely to the improvement of electricity, and indeed of some other branches of philosophical knowledge, than the very ingenious Author of this Article; who here gives us fome electrical observations of a curious and fingular nature : particularly the description of a fimple apparatus, by means of which, the smalleit, and otherwise imperceptible, degrees either of natural or artificial electricity are rendered sensible. What the microscope effects, in bringing to our view bodies otherwise to. tally invisible, is performed by this electrical magnifier, with respect to electricity; by its rendering sensible such small quantities of that fluid, as would otherwise wholly escape the notice of our senses. Nor is this a mere matter of barren curiosity only; but may-it will soon appear that it has already let us

e of the secrets of nature's operations, particularly re

Leorology,

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The apparatus, by which these effects are produced, is no other than the Author's well-known Electrophorus; the refinous coat of which ought to be exceedingly thin (not perhaps above the 50th part of an inch in thickness); and its surface, as well as that of the metal plate adapted to it, should be as plain and as smooth as poffible.

When the sky is perfe&ly clear, and free from electrical clouds, so that an insulated conductor, fitted up to observe the electricity of the atmosphere, does not exhibit the least fign of electricity, by even attracting the finest thread; if a temporary metallic communication be made by means of a wire between the atmospherical conductor and the metal plate, lying on the refinous surface; and this communication be suffered to subfift for a certain time: on removing the wire, the metal plate will, on being lifted up, exhibit evident signs of electricity, by attracting light bodies, and giving sparks. In this case it is sometimes found neceffary to prelerve the communication of the electrophorus with the atmospherical conductor even 8 or 10 minutes. But if the atmospherical conductor alone be capable of barely attracting a light thread; the communication above mentioned need to last a few seconds only: in which time the metal plate will receive, and, as it were, condense such a quantity of electricity, as to dart even a strong spark.

The effects produced by this apparatus appear as extraordinary in discovering the presence of artificial electricity, when it is to weak as to be scarce or at all perceptible by any other means. These appearances too are connected with a hitherto unobserved property of what may be deemed a new class of bodies, such as marble, dry wood, &c. and which may be called semi-conductors, or half-conductors. In this case, the refinous place is not wanted :--but the relation of one experiment will best explain our meaning.

Let a Leyden vial be charged, and then discharged; so that it will scarce affect a light thread : or—as we have varied the experiment, in order to obviate certain objections-let an uncharged Leyden vial be brought to the conductor of an electrical machine; so as to receive from it only two or three moderate fparks. If the metal plate only of the eleEtrophorus (or condenser) be placed on a dry marble flab, a table, or dry piece of wood, or any other imperfe&tly conducting substance, and the knob of the vial be made to touch the metal plate, or, in some cases, to pass over its surface; the latter, on being lifted up, by its intulating handle, will be found to be highly electrified, so as to give very strong fparks : and this it will do repeatedly for some time, on alternately applying the knob of the vial to the metal plate, and then lifting up the latter from the flab, and examining it.

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