50 Mr. W. H. Preece. Effects of Temperature on [Feb. 22, 



pancies that have appeared in the measurements of the behavionr of 

 the Daniell's cell, as well as the erratic performance of batteries 

 used for telegraphic purposes in various exposed positions, have long 

 attracted the attention of the author to the necessity of a more careful 

 enquiry into this matter than has been made hitherto. In fact, all the 

 observations that have hitherto been made are positively useless, from 

 the simple fact that no record has been kept of the independent 

 variations of the internal resistance and the electromotive force in 

 any measurable or comparable manner. 



Special apparatus was made, and the following method of experi- 

 menting was decided upon. 



The cell to be experimented upon was placed inside a cylindrical 

 copper vessel about 10 inches high and about 8 inches diameter; 

 water was poured into the vessel to within an inch of the top of the 

 cell, and the lid of the vessel was put on. 



This lid had four holes, two (insulated from the rest of the vessel) 

 to receive the electrodes of the cell, and the other two to allow ther- 

 mometers to be plunged into the liquid or liquids in the cell without 

 removing the cover or lid. The water in the vessel and the cell in 

 the water were then heated by means of a gas-burner placed under- 

 neath the vessel, and the electromotive force and the resistance of the 

 cell were determined at various stages of the heating; while the 

 temperature of the cell was observed at the time of each experiment, 

 the liquid or liquids in the cell were stirred up from time to time so 

 as to obtain, as far as possible, the true temperature of the cell. 



The cells experimented upon were the Daniell, bichromate, and 

 Leclanche ; those in general use, especially for telegraph purposes. 



The Daniell cell consists of a porous pot, containing a solution of 

 copper sulphate, and placed in a stoneware vessel, containing a 

 solution of zinc sulphate. In the porous pot is immersed a copper 

 plate, bent so as to form a hollow cylinder, to which is soldered a 

 copper wire, which constitutes one pole of the cell. A zinc plate, 

 also bent into a cylindrical form, is placed in the outer cell, and has a 

 copper wire soldered to it, constituting the other pole of the cell. The 

 zinc is not amalgamated. 



Two forms of the bichromate cell were experimented on, the one 

 being that known as Fuller's bichromate cell, and the other that 

 known as single-fluid bichromate cell. The double-fluid cell (Fuller's) 

 consists of a stoneware jar of a quart size. Inside this is placed a 

 porous pot, in which the zinc is placed ; the negative plate, which is 

 of carbon, is placed in the outer jar ; the zinc is cast in the form of 

 a short truncated cone. It is cast on a stout copper wire, both are 

 well amalgamated ; and the plate is surmounted by a terminal. In 

 the outer jar is placed 3 ozs. of bichromate of potassium and 4 ozs. of 

 sulphuric acid. In the inner pot is placed 2 ozs. of mercury. Both 



