Siemens Mercury Unit of Electrical Resistance. 353 



III. were made on other days, when a comparison was made 

 both before and after. The experiments gave the resistance w, 

 or the inductor -f- galvanometer, equal to the following numbers 

 in Siemens's units : — 



I. Temperature of the standard = + 15°*3. 



A -f 0*0071 = 4*1034 Siemens. 



B +0-0111 = 4-1030 „ 



C + 0-0003 = 4-1034 „ 



D + Q-Q113 = 41020 „ 



Mean . w = 4*1029 



Beginning. 



End. 



In Siemens's units, 



Beginning. 



End. 



Mean. 



II. Temp. =+14°8 

 (No. 1135) +01 136 

 (No. 11 43) +0-1 118 



+ 15°-0 



+0-1108 

 + 0-1089 



41062 

 41062 



4-1038 

 41036 



41050 

 41049 



III. Temp. =+13°-8 

 (No. 1135)+01002 

 (No. 1143) +00980 



+ 14°-2 



+01104 



+0-1086 



40915 

 4-0906 



w 



4-1022 

 41019 



= 41049 



4-0968 

 40962 









iv = 4-0965 



VIII. Results. 

 Comparing these resistances expressed in Siemens's units with 

 those expressed in absolute measure, we obtain 



I. 4-1029 Siemens =3-9812 earth -q uad ' . i Siem# =0-9703 



second 

 II. 4-1049 „ =3-9903 „ ; „ =09721 



III. 4-0965 „ =39849 „ ; „ =0'9728 



In the mean, therefore, 



i c«- ) ' L ^ ^*-i~ earth-quadrant . 



1 Siemens's mercury unit = 0°9717 - — -, *. 



* second 



With regard to the ratio of the British-Association unit to 

 Siemens's unit, the most trustworthy value hitherto published 

 is probably that which M. Dehms deduced from a comparison 

 by Mr. Fleeming Jenkin f, 



1 British-Association unit = 1*0493 Siemens, 

 M. Dehms and Mr. Hermann Siemens had the goodness to 

 make at my request a new comparison, from which a British- 

 Association unit (No. 61) belonging to Siemens's laboratory was 



* In the result 09705 {Gbtt. Nach. 18/0, p. 523) an error of calcula- 

 tion had crept in. 



t Pogg. Ann. vol. cxxxvi. p. 404. Report of the British Association, 

 1864, p. 349. Phil. Mag. vol. xxix. p. 4/7. 



Phil. Mag, S. 4. Vol. 47, No. 313. May 1874. 2 A 



