An Essay on Magnetic Attractions, and on the Laws of Terrestrial and Electro Magnetism: Comprising a Popular Course of Curious and Interesting Experiments and the Latter Subject, and an Easy Experimental Method of Correcting the Local Attraction of Vessels on the Compass in All Parts of the World

Front Cover
J. Mawman, 1823 - Compass - 303 pages
 

Other editions - View all

Common terms and phrases

Popular passages

Page 217 - If the uniting wire be placed in a horizontal plane under the magnetic needle, all the effects are the same as when it is above the needle, only they are in an opposite direction; for the pole of the magnetic needle next the negative end of the battery declines to the east.
Page 225 - I was led to consider that all the apparently ' anomalous effects produced on a magnetized needle by the action of a galvanic wire, might be explained by the admission of one simple principle ; viz. that every particle of the galvanic fluid in the conducting wire, acts on every particle of the magnetic fluid in a magnetized needle...
Page 264 - ... so as to project above and below the cork. A little mercury is then poured in, to form a channel between the iron wire and the glass tube. The upper orifice is also closed by a cork, through which a piece of platinum wire passes...
Page 217 - Even glass, metal, and wood, interposed at once, do "not destroy, and indeed scarcely diminish the effect. The disc of the electrophorus, plates of porphyry, a stone-ware vessel, even filled with water, were interposed with the same result. We found the effects unchanged when the needle was included in a brass box filled with water. It is needless to observe that' the transmission of effects through all these matters has never before been observed in electricity and galvanism. The effects, therefore,...
Page 219 - If the uniting wire is bent so as to form two legs parallel to each other, it repels or attracts the magnetic poles according to the different conditions of the case. Suppose the wire placed opposite to either pole of the needle, so that the plane of the parallel legs is perpendicular to the magnetic meridian, and let the eastern leg be united with the negative end, the western leg with the positive end of the battery: in that case the nearest pole will be repelled either to the east or west, according...
Page 216 - If the distance of the joining wire from the magnetic needle does not exceed % of an inch, the declination of the needle makes an angle of about 45°. If the distance is increased the angles decrease as the distances increase. The declination, however, varies according to the efficiency of the apparatus.
Page 117 - As a practical conclusion, it is obvious, that on ship-board, great care ought to be taken to keep the chronometers out of the immediate vicinity of any considerable mass or surface of iron ; on which account they ought not to be kept in the cabins of the gun-roomofficers, which...
Page 276 - Here a brass or copper wire AC, rests at its bent end A, in a cup containing a little mercury, and is very moveable in azimuth round this point. The other end passes through the centre of a circular piece of pasteboard, and then forms spiral turnings in the plane of this circular piece. The wire is attached by thread or silk to the pasteboard disc, and at the point В it turns and descends till its extremity reaches the quicksilver ia the cap D.
Page 226 - I pretend not to illustrate the mechanical principles by which such an action can be produced ; I propose only to show, that if such a force be admitted, all the results obtained from the reciprocal action of a galvanic wire and a magnetized needle may not only be explained, but computed, and that the results agree numerically with experiments.
Page 267 - AC to the other extremity of the battery, whereby the cylinder abcd is made to become a part of the conducting wire, and it will be found to revolve on its axis with a great velocity, fully equal to that of the magnet in the last experiment ; the direction of the motion, with the arrangement shown in the figure, being from left to right, to a person coinciding in position with the magnet.

Bibliographic information