« 



RECENT PEOGEESS IN PHYSICS. 405 



tV same degree of ignition the quotient of the diameter of the wire 

 iro the corresponding force of current should be a constant quantity. 

 Te last column of the previous table contains this quotient. It is : 

 .^'or feeble ignition — 



Deviation from the mean. 



— 0.8 



— 1.0 

 + 1.9 



— 2.8 

 + 13.3 







— 10.5 



— 12.4 



-f 4.9 



— 7.0 

 + 14.7 



For very bright red, nearly white heat — 



0.3 210.0 —10 



0.45 230.0 4- 10 



Mean 220.0 



The deviations from the mean are so irregularly distributed, in 

 ispect to their quantity as well as to their sign, that without hesita- 

 On we may attribute them to errors of observation. That these 

 fjviations are so considerable, varying up to 7 per cent, of the cor- 

 :sponding quotients, will not surprise us if we consider that the 

 'igrees of ignition are not measured, but only estimated. 



A set of experiments similar to the above, with iron wire, gave the 

 llowing results : 



