Harems Calorimotor. 421 



EXPLANATION OF THE PLATE. 



A a, Fig. 1st, two cubical vessels, 20 inches square, inside, 

 b b b b a. frame of wood containing 20 sheets of copper, and 

 20 sheets of zinc, alternating with each other, and about half 

 an inch apart. T T 1 1 masses of tin cast over the protruding 

 edges of the sheets which are to communicate with each other. 

 Fig. 2, represents the mode in which the junction between 

 the various sheets and tin masses is effected. Between the 

 letters z z, the zinc only is in contact with the tin masses. 

 Between c c the copper 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 between z z, are made to commu- 

 nicate, by a common mass of tin extending the whole length of 

 the frame, between T T : but in front, as in fig. 1, 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 tin masses, may be seen 

 on either side of the interstice : and likewise a wire for 

 ignition held between them. The application of the rope, 

 pulley, 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 p p there is a wooden partition which 

 is not necessary, though it may be beneficial. 



Fig. 3, represents an apparatus alluded to, page 419. It 

 consists of a couronne des tasses, reduced to a form no less 

 compact than that of the trough. Hollow parallelopipeds of 

 glass are substituted for tumblers or cells. The plates are 

 suspended to bars counterpoised like window-sashes. 



The advantages are as follows. The material is one of the 

 best non-conductors, is easily cleansed, and is the most imper- 

 vious to solvents. The fracture of one of the cups is easily 

 remedied by a supernumerary. They may be procured (as 

 in the United States) where porcelain cannot be had. The 

 shock from 300 pairs is such as few will take a second time. 

 Some of the effects have already been stated.* 



At Fig. 4, one of the hollow glass parallelopipeds on an 



enlarged scale is represented. 



* The glasses may be had by applying to Edw. A. Pearson, No. 71 Cornhill, 

 Boston. 



