152 Electromotive Force of different Forms of the Clark Cell. 



cells made by tlie fourth-year class of electrical students during the 

 session of 1896-1897. These cells were all of the portable B.O.T. 

 form, with a flattened and amalgamated platinum wire in place of 

 mercury. They were set up in test-tubes, filled with crystals, and 

 sealed with marine glue, and were otherwise exactly similar to the 

 crystal cells described in § 10. 



With the exception of those marked with an asterisk, the observa- 

 tions were all taken by the students themselves in the coarse of an 

 afternoon's work. Readings were taken at the points 15°, 0°, 15°, 

 30°, 15°, allowing only about half an hour at each temperature. 



Table VIII. — Portable Crystal Cells, made by Students. 





Date 



Date 



Difference 



Change of E. 



M.F. 



Mean 



Name of student. 



when 

 made. 



when 

 tested. 



from 

 standard 

 at 15°. 



0°- 



-15°. 



15°- 



-30°. 



change 



per 

 degree. 



Stovel 



Mar. 2 . . 



Mar. 4 . . 



-0-17 



16 



•57 



19 



•39* 



1 



199 



Thomson 



Mar. 2 . . 



Mar. 4 . , 



-0-11 



16 



•60 



19 



38 



1 



•199 



Blair 



Feb. 19 . 



Feb. 21 . 



+ 0-05 



16 



63 



19 



41 



1 



•201 





Dec. 8 . . 



Jan. 19 . 



-0-02 



16 



•57 



19 



•30* 



1 



196 



Davidson 



Jan. 12. . 



Jan. 19 . 



+ 0-11 



16 



•62 



19 



•40 



1 



•201 





Dec. 10 . 



Jan. 26 - 



+ 0-07 



16 



•60* 



19 



•36* 



1 



•199 





Dec. 3 . . 



Dec. 8 . . 



-0-04 



16 



62 



19 



•36 



1 



•199 



McDonald, P. W. 



Jan. 14 



Jan. 19 . 



+ 0-14 



16 



•63 



19 



•49 



1 



•204 



McDonald, J. E. 



Feb. 19 . 



Feb. 21 . 



-0-15 



16 



•58 



19 



•30 



1 



•196 





Jan. 12 



Jan. 19 . 



+ 0-14 



16 



56 



19 



•43 



1 



•200 





Dec. 10 . 



Jan. 26 . 



+ 0-05 



16 



•58* 



19 



•53 



1 



•204 





Dec. 3 . 



Dec. 8 . 



-0-13 



16 



•61 



19 



•44 



1 



•202 





-0-005 



16 



•603 



19 



400 



1 



•2000 



It should be observed that the cells were, in most cases, tested 

 rather too soon after being sealed up. In the course of a week or 

 two, they were usually found to have settled down into closer agree- 

 ment with the standard. When kept for a longer time than half an 

 hour at 30° C, they showed a slightly greater change of E.M.F. at 

 this point. 



