Elements of electricity, magnetism, and electro-magnetism : embracing the late discoveries and improvements : digested into the form of a treatise, being the second part of a course of natural philosophy : compiled for the use of the students of the University at Cambridge, New England / by John Farrar.

John Farrar

Date:: 1826

Credit: Elements of electricity, magnetism, and electro-magnetism : embracing the late discoveries and improvements : digested into the form of a treatise, being the second part of a course of natural philosophy : compiled for the use of the students of the University at Cambridge, New England / by John Farrar. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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houses on which they were erected had in consequence been struck by lightning. [The original memoir of M. Guy-Lussac not being at hand, the above was extracted with a few alterations from a translation con- tained in the Annals of Philosophy.'] III. Hare-s Calorimotor and Deflagrator. 1. Calorimotor. This name is given by Dr Hare to an instrument invented by him in which the calorific eifects are accompanied with a feeble influ- ence upon the electroscope. Fjg.-74. u .;5, a, represent two cubical vessels twenty inches square, h bhh a frame of wood containing twenty sheets of copper, and twenty sheets of zinc, alternating with each other, and about half an inch apart, TTtt, masses of tin cast over the protruding edges of the sheets, which are to communicate with each other. Fig. 74' represents the mode in which the junction between the several sheets and the tin masses is effected. Between the letters z z, the zinc only is in contact with the tin masses. Between c c, the cop- per alone touches. It may be observed, that, at the back of the frame, ten sheets of copper between c c, and ten sheets of zinc be- tween z z^ are made to communicate by a common mass of tin ex- tending the whole length of the frame between TT; but in front, as shown in figure 74, there is an interstice between the mass of tin, connecting the ten copper sheets, and that connecting the ten zinc sheets. The screw forceps, appertaining to each of the ten masses, may be seen on either side of the interstice; and likewise a wire for ignition held between them. The application of the rope, pul- ley, and weights is obvious. The swivel at S permits the frame to be swung round and lowered into water in the vessel a, to wash off the acid, which, after immersion in the other vessel, might continue to act on the sheets, encrusting them with oxide. Between pp, there is a wooden partition which is not necessary, though it may be beneficial. Volta considered all galvanic apparatus, says Dr Hare, as consisting of one or more electromotors, or movers of the electric fluid. To me it aj>peared, that they were movers of both heat and electricity ; the ratio of the quantity of the latter put in motion, to

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