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water only, I repeated the above experiments on green and dry vegetables with a red-hot earthen crucible, but without any difference in the result. A square piece of brick was first placed upon the electrometer, to prevent the heat from injuring it in this and all the subsequent experiments, in which red-hot bodies were to be placed
16.-A spoonful of salt was thrown into the red-hot crucible, which opened the gold leaf negatively; a second quantity was thrown in, and it became positive.
17.—The crucible being again heated, two spoonfuls of salt were thrown in, which opened the gold leaf positively; then water was dropped into the middle of the salt, which changed its electricity to negative; then more water dropped near the side of the crucible opened the gold leaf positively; then again in the middle negatively.
18.–Salt and water were mixed and dropped into the red-hot crucible, which caused a strong negative repulsion; then, after the water was evaporated, more was dropped in the middle, which renewed the negative repulsion till the water was dropped near the side, when it became positive. This change from positive to negative was often repeated.
19.—A small quantity of salt was thrown into the red-hot crucible, which caused the gold leaf to open negatively; then the salt remained till it was burnt black, and water being added, caused a strong positive repulsion.
20. --The vitriolic and nitrous acids were severally dropped upon red-hot bricks, which opened the gold leaf positively. The bricks were tried before and after the experiments with water, which caused a negative repulsion.
21.–A large red-hot cinder was placed upon the electrometer, and olive oil dropped upon it, producing a copious smoke, but no electricity; then water was added, which opened the gold leaf negatively.
22.-Olive oil and water were shook together in a phial, and both poured upon a red-hot piece of cast iron about an inch thick, four inches broad, and five inches long, which opened the gold leaf strongly negative.
23.–Vitriolic and nitrous acid were dropped upon the cast iron, which opened the gold leaf positively.
24.—Dry hay was placed upon the cast iron, and pressed down by a stone placed upon it till it was burnt black ; then water was added, which opened the gold leave positively. The hay was then brushed off, and more water dropped upon the iron, which caused the gold leaf to open positively till the surface was well cleaned and heated again, when it produced negative.
25.-A heap of wheat flour was placed upon the hot iron, which smoked without any electricity till water was added, which opened the gold leaf positively.
26.-Sand placed upon the hot iron, and water added, opened the gold leaf positively.
27.-Lump sugar placed upon the hot iron produced no electricity till water was added to the burnt residuum, which opened the gold leaf positively.
28.—Powdered charcoal was placed upon the hot iron, and water poured upon it opened the gold leaf positively; but when water was dropped upon a red-hot piece of charcoal, it caused a negative repulsion.
29.-Red and white port wine dropped upon the hot iron produced negative repulsion when the iron was so hot as to produce no electricity with water alone, which was tried before and after the wine.
30.—Raspberry wine dropped upon the hot iron produced positive electricity. The raspberry wine and red port were alternately dropped upon the same iron five or six times successively, which changed the electricity from positive to negative each time. Also several other sweet wines were tried, which, as well as sugar and water, produced positive electricity.
31.–Fresh urine poured upon the hot iron produced strong positive electricity.
32.—Milk poured upon the hot iron caused a strong negative repulsion ; and even when water was added to the burnt residuum, except in some instances when it was burnt very black, it became weakly positive.
33.—Butter was burnt upon the hot iron, and water added caused a strong negative repulsion.
34.-Ale produced no electricity till water was added to the burnt residuum, which became positive.
35.-Dry tea leaves were burnt upon the hot iron, and water added opened the gold leaf positively; also black pepper and tobacco.
36.–Soap first burnt on the hot iron, and then water added; also soap and water mixed produced a strong negative repulsion.
37.-Tin-foil was placed upon the hot iron, which soon melted ; then water dropped upon it first opened the gold leaf negatively, then weakly positive.
38.-Alum burning on the hot iron produced no electricity till water was added to the burnt residuum, which caused a strong positive repulsion.
39.—Moist salt of tartar was thrown upon the hot iron, which caused the gold leaf to open strongly negative ; its vapours condensed so quick upon the tube used for trying the electricity, that it was with some difficulty that it could be excited.
40.-Saliva produced positive electricity. When water alone was producing negative repulsion, spitting upon it would immediately change it to positive.
41.-Yeast was strongly positive, but not till water was added to the burnt residuum.
42.-Cotton and linen rags were burnt on the hot iron, and water added, produced a weak positive repulsion.
43.--Sheep's wool, feathers, and hair, were burnt on the hot iron, and when a single drop of water was added, the gold leaf struck the sides of the electrometer positively.
44.— Rasped horn and bone were burnt upon the hot iron, which produced positive electricity when water was added, but not near so strong as in the last experiment.
45.- Powdered pit coal was placed upon the hot iron, which produced positive electricity upon the addition of water.
46.- Fresh sheep's blood was dropped upon the hot iron, which produced positive electricity.
47.--A hollow piece of bell metal about an inch thick, and three inches diameter, was cast on purpose to repeat these experiments upon, most of which were again tried, but with no remarkable difference, except that water produced negative electricity with more certainty. Upon the iron it was sometiines negative, sometimes positive, but mostly none at all; whereas on the bell metal it was almost always negative.
48.- Vinegar produced no electricity when dropped upon the hot bell metal, till water was added to the burnt residuum, which caused a strong positive repulsion.
49.—The bell metal was at last made too hot, and therefore broke to pieces as it was taken out of the fire; I therefore again had recourse to cast iron, and for the sake of its holding fluid substances, I turned a cast metal weight so as to have a very smooth concave surface in the middle, and a concave rim near the edge, so that I could place upon it several substances at once, without mixing. The lean part of a leg of veal was chopped small, and a small quantity placed upon the red-hot cast iron, which caused the gold leaf to open positively, but after burning some time, water was added, which changed its electricity.
50.—The fat of veal was burnt upon the hot iron, which produced no electricity till water was added, which caused a strong negative repulsion both before and after it was burnt black.
51.-Nitre was put upon the hot iron, which melted without producing electricity; then water was dropped upon it, which exploded without producing any electricity; sometimes small globules of water floated a considerable time upon the melted nitre, and then suddenly exploded without ever producing any electrical repulsion or gradual evaporation, as is usual with other substances.
52.-Bees wax produced strong negative electricity, with the addition of water.
53.–Verdigrease with water produced very weak positive electricity.
54.- Powdered antimony smoked much, and when water was added the gold leaf opened negatively.
55.-Carraway seeds dropped upon the hot iron caused a strong negative repulsion without the addition of water, also water added
when they were burnt black opened the electrometer negatively.
56.—Hemp seed thrown upon the bot iron caused a weak positive repulsion, but when water was added it became strongly positive.
57.–A tea spoonful of water was dropped into the concave hot iron which did not produce any repulsion, then some powdered gum arabic was added, which caused the gold leaf to diverge positively, then bees wax was also added, which caused it to become negative.
58.—These two last substances were dropped on the hot iron in the reversed order, which first produced negative and then positive.
59.—Mustard seed was dropped upon the hot iron, which caused no repulsion till water was added to the burnt residuum, which opened the gold leaf negatively.
60.-Linseed produced no electricity till water was added to the black residuum, which opened the electrometer weakly negative. The iron was then made hotter, and the addition of water produced positive.
61.-Canary seed also produced negative by the addition of water till it was burnt very black, and then it became positive; also anise seed, and fennel seed, were like the canary.
62.-Burnt millet seed produced positive electricity with the addition of water.
63.—Water added to burnt coriander and cummin seeds produced negative electricity till the residuum had continued burning a long time, and then it became positive.
64.-Hitherto the electricity of the apparatus whence the vapours ascend has been oply examined. I now fastened a piece of paper upon a bent wire, which being placed in the cap of the electrometer hung over the hot iron, so that the vapours in ascending might pass over the paper, and shew whether this electrical state would in any
instance be of the same kind observed in the vessel.
65.—The vapour of red port wine was tried as above, and found positive, contrary to the state of the iron in exp. 29.
66.— The vapour of raspberry wine was found to be negative contrary to the state of the iron in exp. 30. Also wine made from bilberries, and sugar and water mixed, produced negative vapours.
67.—The vapour of pure water was positive, but the addition of a small quantity of saliva changed it to negative. 68.- 'The vapour
of raisin wine was first positive and then negative, and the reverse when the iron was examined.
69.- As carraway seed produced negative electricity without the addition of water, and therefore without any visible vapour, except a little smoke, the paper fixed upon the electrometer was several times placed at different distances above the hot iron, whilst the carraway seeds were burning, but no electricity appeared.
70.–The square brick which supported the hot iron was placeil in the middle of an earthen plate full of water, and standing upon the electrometer, then the hot iron being laid upon the brick and out of the reach of the water, wool was burnt upon it, and a spoonful of water added; lastly, the whole was covered with a glass jar
with its mouth immersed in the water, that the vapour might not escape without touching the water; in this experiment no electricity appeared.
From these experiments it appears that various mineral, vegetable, and animal substances when evaporated, cause a positive or negative divergency of the electrometer, and it was remarked, in the beginning of this section, that M. de Saussure attributed these effects to the generation of a new quantity of the electrical fluid; but since the state of the electricity of the ascending vapour is contrary to that of the insulated vessel whence it rises, it now seems more probable that the vapour thus produced acquires its positive or negative state because its affinity with the electrical fluid is greater or less than that of the vessel, and that when a particle of vapour is but just in contact with the surface whence it rises, its capacity to become positive or negative is much greater than when it is entirely surrounded with air; and thus if the vapour becomes positive by absorbing electricity from the vessel, the vessel will become negative, and v. v., without the necessity of supposing a new quantity of the Auid to be generated in this process.
The above extensive experiments of Mr. Bennet, which were, no doubt, made with great care, are not attended with those uniform results as might have been expected, from the views we have hitherto taken on this subject; and it is probable that those aberrations which are so conspicuous in several cases, might be traced to some other cause than that of simple evaporation, but as we have not yet repeated these experiments, any further remarks on them, in this place, would certainly be premature.
EXPERIMENTS BY DR. CHARLES SCHAFHAENTL. The experiments of this gentleman were made in the Royal Adelaide Gallery, and in consequence of his considering that the electric phenomena of steam boilers being dependent on the incrustations which they contain, he selected one of Marcet's common boilers, in preference to one of Mr. Perkins's kind, in which incrustation is prevented. The boiler selected was globular, of iron, and about five inches diameter. In the vertical axis of this experimental boiler was a mercurial guage, and at the distance of about 45° from it, downwards, was a thermometer; and on the opposite side of the globe, a jet with a stopcock. The lower part of the cavity of the boiler was occupied by the mercury belonging to the steam guage, and on the top of this mercury an inch and a quarter deep of distilled water was placed. A glass bell, nine inches diameter, and five inches deep, was suspended with its axis in the axis of the jet continued, having the muzzle in the direction of the jet, at about four inches distance. The greater portion of
bundle of copper wire was inserted in the bell, and the remote end of the wire was connected with a gold leaf electroscope, furnished with a condenser. When the water in the globe had boiled to a sufficient extent to raise the mercurial gage to thirty-one inches, the stopcock of the jet was