412 All Account of some Experimenls 



supposition alluded to, they ought to be inferior. From the 

 foregoing results, the order of the conducting powers of the me- 

 tals tried is silver, zinc, gold, copper, iron, and platina. Tin 

 and lead fuse so immediately at the point of contact, that they 

 cannot be placed. Between gold and copper the. difference is 

 trifling ; and with regard to platina and iron, their relations to 

 each other, in this circumstance, seem to be aflfected by elevation 

 of temperature. It may be observed, that the order of the above 

 metals, as conductors of electricity, nearly follows that of their 

 powers to conduct heat. 



In an experiment in which equal lengths of two platina wires, 

 of unequal diameter, (the larger being -^-^Xh, the smaller -J^lh. of 

 ru inch,) were placed together in the circuit parallel to each 

 other, the thicker wire was ignited, because it conveyed more 

 electricity without proportional increase of cooling surface. When 

 connected continuously, the order of ignition was reversed. 

 These two results were foreseen, by Dr. Wollaston, who suggested 

 the experiments. 



The experiments which 1 now proceed to mention, were made 

 with the battery in a high state of excitation ; and I consider 

 them as representing nearly the maximum of eifect which it is 

 capable of producing. As the quantity of acid was increased 

 from time to time, and that previously added often almost spent 

 before fresh was put in, it is not easy to say exactly what pro- 

 portion it bore to the water ; perhaps the largest may be stated 

 •At about 4g\h. On this, as on former occasions, I found a mix- 

 ture of nitrous and sulphuric acids, to produce the most power- 

 ful and permanent effects. 



Exp. 1 . 5 ft. 6 in. of platina wire, -^-^ of an inch in diame- 

 ter, were heated red throughout, visible in full day- light. 



Exp. 2. 8 ft. 6 in. of platina wire, -^W of an inch in diame- 

 ter, were heated red. 



Exp. 3. A bar of platina l-6th of an inch square, and 2| 

 inches long, was also heated red, and fused at the end j and, 



Exp. 4, a round bar of the same metal, -Vo'V of an inch in 

 diameter, and 2[ inches in length, was heated bright red through- 

 out. 



Exp. 5. Fine points of boxwood charcoal intensely ignited 

 in chlorine, neither suffered any change, nor produced any in 

 the gas. The result was similar when heated in azote. 



I next tried the power of the battery to fuse several refractory 

 substances. The subject of experiment was placed in a small 

 cavity, made in a piece of well burnt boxwood charcoal, floating 

 on the surface of the mercury in one of the basins before men- 

 tioned, and the circuit completed by another piece of charcoal, 

 connnunicating by stout copper wire, with the other basin. 



Exp. 



