ON STANDARDS OF ELECTRICAL RESISTANCE. 



519 



2nd. The coil of the 3rd series was, in the unprotected state, immersed 

 in distilled water, and compared with many hundred yards of thick copper wire, 

 unimmersed, having nearly equal resistance. The result showed that the 

 resistance to the current was sensibly the same whether a single cell or five 

 cells of Daniell in a series were used. Now, had any considerable leakage 

 by electrolytic action taken place, it would have been very much less in pro- 

 portion in the former than in the latter instance. 



3rd. When the coils of the second and third series, in the unprotected state, 

 were placed in distilled water, and made the electrodes of a battery of five 

 cells, the deflection was 40' of a degree on a galvanometer with a coil of 

 17 inches diameter composed of 18 turns of wire. This deflection indicates 

 a current of about -^^ of the average current in the thermal experiments. 

 In this case the chemical action was distinctly visible, but quite ceased to be 

 so when the electrodes were connected by a wire of unit resistance, so as to 

 reduce the potential to that in the thermal experiments. 



4th. The coil of No. 2 series being used as a standard, that of No. 3 

 series, in the unprotected condition, was immersed, first in water, then in 

 oil. The resistance to the current of five DanieU's cells was found to be 

 sensibly equal in the two cases. 



Hence there could be no doubt that the loss of heat during the experi- 

 ments by electrolytic action could not possibly in any instance have been so 

 great as one-thousandth of the entire efi'ect, and was probably not one 

 quarter of that small quantity ; whilst in the larger number of experiments, 

 when the varnish was fresh, it must have been nil. 



The coil used in the third series of experiments was made by bending 

 four yards of platinum-silver wire double, and then coihng it into a spiral 

 which was supported and kept in shape by beiag tied with silk thread to a 

 thin glass tube. ' The terminals were thick copper wires, and the whole was 

 coated with shellac and mastic varnish. The following results were ob- 

 tained for its resistance. In the first three trials the current was measured 

 by a galvanometer with a circle of nine turns 17 inches diameter, and in the 

 last six with an instrument with eighteen turns of wire. In the first six 

 there was an extra unit of resistance included in the circuit : — 



Battery. 



Unit. 



C,. 



Temp. 



of 



unit. 



Temp. 



of 



coil. 



Resistance 



in terms of 



my unit. 



One cell, Daniell . . 



Ditto 



Ditto 



DanieU's cell. Posi- 

 tive metal iron . . , 



Ditto 



Ditto 



Ditto 



Ditto 



Ditto 



Mine ... 



>) • • • 



Jenkin's 



Mine ... 



Jenkin's 

 Mine ... 



tan 52 53 

 tau 52 24" iz 

 tan 52 3'62 



tan 50 a5'8 

 tan 49 48' 1 2 

 tan 48 17-62 

 tan 75 28 

 tan 75 i7'2 5 

 tan 75 59'6 



tan 37 3-15 

 tan 36 29-02 

 tan 36 6'45 



tan 35 21-88 

 tan 34 57-36 

 tan 34 5-48 

 tan 49 586 

 tan 49 44-93 

 tan 49 18 97 



Average 



o / 



tan 37 10-6 



tan 36 37-27 



tan 36 14-79 



tan 35 29-27 



tan 35 5-62 



tan 34 12-24 



tan 50 11-98 



tan 49 57-51 



tan 49 3 3 '08 



63-27 

 59-03 

 6o-88 



59-78 

 6003 

 60-50 

 61-27 

 6196 

 6935 



62-78 

 60-07 

 60-57 



60-46 

 60-30 

 6088 

 61-08 

 61-27 

 70-28 



-98963 

 •98823 

 -98752 



•98818 



■98754 

 •98816 

 •98863 

 •98871 

 -98820 



•98831 



The above average resistance, reduced to 18°-63 C, the mean temperature 

 in the third series, is -98953 of the Association unit, or in British measure 

 32465180. 



In the third series, the experiments for the heat of the current, of radia- 



