Intelligence and Miscellaneous Articles. 161 



For the Daniell's element the following values were found : — 





Newly filled. 



After 15 minutes' 

 use. 



Mean. 



I 



i 

 L 

 E 



1540 



71-0 



9-2 



2108-0 



141-7 



69-2 



10-8 



21640 



100 



2136-0 



In the experiments with the above-described plate of copper pyrites 

 four different but constant applications of heat were tried. The fol- 

 lowing series of results were obtained (arranged according to ascend- 

 ing degrees of applied heat): — 





First. 



Second. 



Third. 



Fourth. 



I 



98-9 



116-0 



134-5 



150-5 



i 



41-8 



50-7 



56-7 



63-5 



L 



7-4 



7-9 



72 



72 



E 



145-4 



180-2 



196-0 



218-8 



E (ther. elec.) 



1 



1 



1 



1 



E (Daniell) 



14-7 



11-9 



10-9 



9-7 



L (ther. elec.) 

 L (Daniell) 



0-74 



0-79 



0-72 



0-72 



During the experiments the heat of the water used for cooling 

 rose somewhat over 60° C, and then remained constant at this tem- 

 perature. Although the copper pyrites was heated above the tempe- 

 rature of melting tin, no change was observed either in its interior or 

 on the cut surfaces of the holes pierced through it. In order not to 

 split the apparatus, I did not apply a higher temperature ; for it was 

 manifest, from the loosening of the copper pins during the process of 

 cooling, that, when heated, the latter metal expanded more than the 

 pyrites. A still greater electromotive force, however, might readily 

 be obtained by raising the temperature, provided the consequences 

 of unequal expansion were guarded against by cutting the pin, lon- 

 gitudinally, with a saw down to its axis, and thus enabling it, in vir- 

 tue of its elasticity, to accommodate itself to the aperture. But even 

 at the temperature to which it was exposed, this small pile exhibited 

 a ten times greater action than a bismuth and antimony element, 

 of equal effective resistance, when heated from 0° to 100° C. Ten of 

 the above-described pairs formed into a battery suffice to give all the 

 actions of a Daniell's element, containing an effective copper surface 

 14 square centimetres in area. 



Copper pyrites in its natural state melts easily, at a strongly glow- 

 ing heat, without sensible decomposition ; and it may then be cast 

 in any mould whatever. It is a remarkable fact, however, that this 

 substance thereby suffers a change, in consequence of which it 

 sinks far below bismuth in the thermo-electric tension series. Con- 

 sequently it is only the mineral in its natural state which can be 



Phil. Mag. S. 4. Vol. 29. No. 194. Feb. 1865. M 



