The book of philosophical experiments, illustrating the principal facts and curious phenomena of electricity, galvanism, magnetism, optics, chemistry, heat, etc., with introductory observations of each science, and upwards of 300 experiments.

  • Dalton, J. S. (John S.)
Date:
[1839?]
Catalogue details

Licence: Public Domain Mark

Credit: The book of philosophical experiments, illustrating the principal facts and curious phenomena of electricity, galvanism, magnetism, optics, chemistry, heat, etc., with introductory observations of each science, and upwards of 300 experiments. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    that he possesses the power of commanding the watch to stop, or go, at his pleasure. For this purpose, a magnet must be fixed underneath the top of the table, and a mark made on the table immediately above it; then if the watch be laid on this spot, the magnet will attract the steel e-wheel, and atop the watch. Directly the magnet is moved, the watch will again go on, and thus it may be made to stop or go, at the pleasure of the experimenter. More surprise will be created if, after having removed the magnet from under the table, another person be requested to try whether his placing it on the table will have any effect, which, of course, will not be the case while the magnet is removed. This experiment is a very old one, but it illus- trates how easily chronometers may be affected by accidental causes ; and sometimes the mari- ner's compass itself loses its power, in conse- t>f superior magnetic influence, occasion- ed by having particular substances on board a ship. TO SHOW MAGNETIC ATTRACTION'. 74. If a magnet be brought into contact with some iron-tilings, they will adhere to it. The filings are strongly attracted to each pole, but none of them to the centre of the bar. It appears, from this circumstance, that the magnetic power re- sides chiefly in the poles, and that there is a part of the magnet, generally midway between them, where little or no attractive power is exerted. 75. The north or south pole of one magnet re- pels the north or south pole of another, just as bodies similarly electrified repel each other. If a magnet be dipped in iron-filings, they will im- mediately become attached to one end. Suppo- sing this to be the north pole, each of the ends of the filings, not in contact with the magnet, will become north poles; while the ends in con- tact will, by induction, become south poles. Both of these will have a tendency to repel each other, and the filings will, therefore, stand on the mag- net. The ends of the filings in contact cannot eh other, because they arc so strongly at- (racted by the pole of the magnet; but at their other ends, where this force is not exerted, they do repel each other, showing that they are in the same magnetic state. roLARITV OF THE MAGNET. 7G. If a piece of steel, that has been rendered magnetic, be supported so that it can turn freely, it is found to point with one end to the north, and the other to the south (see Introduction.) This property may be pleasingly illustrated, by tying a magnetised piece of steel round its centre with a piece of sewing silk, and supporting it from a Stand, as the pith balls are supported in a pre- vious experiment. Another method is, to place a inagnet on a piece of cork swimming in a basin of water. If tin- cork be placed in the centre of the basin, so that it is not attracted by the sides, the magnet will be found to turn due north and south, the same as the mariner's compass, which of accident at sea, it might be made to supply the place of. HOW TO .MAKE A MAGNET BY GALVANISM. 77. As mentioned in the Introduction, Galvan- ism is capable of forming magnea out of com- mon steel. To effect this, make a connection between the poles of an excited battery with the two ends of a wire formed into a spiral coil, by bending common bonnet wire closely round a cyl- inder, or tube, of about an inch in diameter ; in- to this coil introduce a needle, or piece of steel wire, laying it lengthways down the circles of the coil. In a few minutes after the electric fluid has passed through the spiral wire, and, consequently, round the needle or wire, the latter will be found to be strongly magnetised, and to possess all the properties of a strong magnet. 78. The same effect may be produced by pass- ing a charge through this spiral coil from an elec- trical battery. EFFECT OF A CURRENT OF ELECTRICITY ON A MAGNET. 79. If a current of electricity be made to pass along a wire, under which, in a line with it, a compass is placed, it will be found that the needle will no longer point north and south, but will take a direction nearly across the current, and point almost east and west. This fact has led philos- ophers to believe, that there are constant currents of electricity passing cast and west across the earth, and which, therefore, cause the needle uni- formly to point to the north. CHEMISTRY. Inn iln, tion in tin- senile, of < luinistry—Chemical affinity explained and illustrated—The i-uvets it produces—Dif- ference between .in element and a compound—Tlie laws I' chemical combination explained—Wonderful ef- fects of these laws—Production of poisons from harmless elements—change of color from combination—Change of bulk from ditto—Crystallization—The atomic theory ex- plained. 80. There arc no experiments more pleasing, more instructive, or more easily performed, than those which illustrate the leading principles of the science of Chemistry ; and as a knowledge of them may frequently be of eminent service in preventing dangerous accidents, and of great use in many little domestic operations, we have made a numerous collection of the more pleasing and entertaining, and arranged them so that they il- lustrate all the leading facts in a simple manner. To perform them, it is not necessary to purchase expensive apparatus; for indeed, the whole of them may be illustrated for a few shillings, and the more simple the apparatus, the less danger there is of the experiments failing. Sir Hum- phrey Davey taught himself chemistry with ap- paratus, that did not cost him more than a few shillings ! and the student, who wishes to perform the experiments which follow need not, therefore, fear that the means of doing so are beyond his reach. The best way to begin it is to purchase the smallest quantity of the chemicals that can be obtained ; for an experiment may, in general, be tried just as well with a small, as with a large quantity ; and if it is obtained pure, from a good operative chemist's, the less that is used the bet- ter. Then for apparatus, ;i few slips of common window glass, which may be obtained at any glazier's for a few pence, will answer every pur- pose. Chemical mixtures, of all kinds, may be made on a slip, by adding two or three drops of the liquids together, and the effect will be seen quite as well as if they were mixed