44 Miss Marshall and Dr. Ramsay on the Heats of 



Table III. 



Substance. '. 



Date. 



Eatio ^1. 



L 2 



L r 



Water Ju 



Iy2. 

 , 6. 

 , 11. 

 , 18. 

 , 19. 

 , 19. 

 , 12. 

 , 13. 

 , 20. 

 , 23. 

 , 24. 

 , 25. 



0-391 "1 

 0390 } 

 0-391 J 

 0355 1 

 0363 J- 

 0-358 J 

 0-398 

 0-398 

 0-392 

 0-392 

 0-471 

 0484 



209-74 



75-2 



83-5 



82-2 



100-2 





" 



Chlorobenzene , 





" 



Ether 



Ethyl Acetate , 











8. Third Series of Experiments. February 1895. 



In the early part of this year the apparatus was further 

 modified with a view to increasing the accuracy of the re- 

 sistance measurements. 



The readings of resistance had been found very troublesome 

 and very uncertain. In many experiments it was almost 

 impossible to obtain anything like a point of balance on the 

 bridge-wire : it was useless to attempt to read to within 

 1 centim. length of the wire ; and during anyone experiment 

 the points of balance did not remain steady at all, but seemed 

 to shift indefinitely. This might be the consequence either 

 of variations in the strength of the current in the main 

 circuit, or of change in the resistance of the bridge -wire from 

 unequal heating. [The bridge consisted of a coil of un- 

 covered platinoid wire immersed in cold water and connected 

 in series with a platinum wire stretched against a scale.] 

 Probably both causes were working together. 



Two important changes were made : — 



(i.) The current in the primary or lamp- circuit was taken 

 from 8 secondary cells, instead of being taken from the mains 

 through a (probably) variable resistance. 



(ii.) A new bridge was made, consisting of four parallel 

 german-silver wires of approximately equal resistance stretched 

 against four metre-scales. 



The whole of the resistance in the secondary circuit now 

 falls into the bridge itself ; whatever heating- effect there may 

 be is distributed all along the bridge, and its effect is much 

 lessened if not altogether removed. The resistance of the 

 bridge-wire does not need to be known, provided it is tolerably 



