282 Hf. A. Rowland—Absoiute Unit of Electrical Resistance. 
sary to select a region entirely free from such disturbance. 
The small probable error proves that sufficient precaution was 
taken in this respect. a 
The result of the experiment that the British Association 
unit is too great by about ‘88 per cent, agrees well with Joule’s 
experiment on the heat generated in a wire by a current, and 
makes the mechanical equivalent as thus obtained very nearly 
that which he found from friction: it is intermediate between 
the result of Lorenz and the British Association Committee; 
and it agrees almost exactly with the British Association Com- 
mittee's experiments, if we accept the correction which I have 
applied below. 
The difference of nearly three per cent which remains be- 
tween my result and that of Kohlrausch is difficult to explain, 
but it is thought that something has been done in this direc- 
tion in the criticism of his method and results which are en- 
tered into below. My value, when introduced into Thomson’s 
light: but experiments on this ratio have not yet attained the 
highest accuracy. 
History. 
The first determination of the resistance of a wire in absolute 
stan stance. However we know that the wire was of 
copper and the temperature 0° R. and that the result obtained 
* Bestimmung der Constanten von welcher die Intensitat inducirter elektrischer 
Stréme abhangt. Pogg. Ann, Bd. 76, S. 412, 
+ Elektrodynamische Maasbestimmungen; or Pogg. Ann., Bd. 82, 8. 337. 
