Intelligence and Miscellaneous Articles. 225 



The driving forward of the oxyhydrogen gas here supposed has 

 also been assumed by Mallard and Le Chatelier*, in order to explain 

 the increase of the velocity of propagation of the ignition observed 

 by them. 



From what has been adduced, it follows, inter alia, that in pre- 

 cise determinations of the heat of formation of water the H 2 2 

 formed must also be taken into account, and, further, that, in the 

 case of explosion, the loss of heat occasioned by the breaking must 

 be taken into consideration. — Wiedemann's Annalen, 18S2, no. 2, 

 vol. xv. pp. 289-292. 



ON THE LAW OF RADIATION". BY J. VIOLLE. 



The intensity of a simple radiation emitted by incandescent pla- 

 tinum is very accurately represented by the formula 

 I=mT 3 (l + ea- T ) T , 



as I have previously pointed out, and as is proved by the following 

 Table, which contains the values calculated by means of this for- 

 mula for a portion of the measure tnents before mentioned : — 



t. 



, ftKfi f 6=0-041495 

 A_Mb la=l-00045. 



x _x Sq . 9 r 6=0-04295 

 X - 5892 {a = 1-00044. 



r e=0-04467 

 X=53 °ta = 100043. 



Calculated 

 intensities. 



Differences 

 from the 

 observed. 



Calculated 

 intensities. 



Differences 

 from the 

 observed. 



Calculated 

 intensities. 



Differences 

 from the 

 observed. 



o 



Tib 

 954 

 1045 

 1500 

 1775 



"l 

 3-1 

 153 



501 



"6 

 -0-2 





 -6 



005 



1 



3-4 

 218 

 812 











-0-2 



-1 

 +3 



1 

 3-6 



324 

 1365 



"6 



- 0-1 



+ 17 

 



But if the attempt be made to represent by the same formula 

 the numbers of Dulong and Petit relative to the radiation of their 

 thermometer between 80° and 240°, good results are not obtained. 

 Nor does the celebrated formula of those two physicists, I=ma*, 

 agree with the measurements obtained with incandescent platinum ; 

 and the expression I=mT 4 , recently proposed by M. Stephan, 

 giving for the relative intensities at 954°, 1045°, 1500°, and 1775° 

 the numbers 1, 1-33, 4-36, and 7*73, cannot be adopted. 



On the other hand, a very satisfactory representation of the 

 whole of the measurements is obtained by means of the formula 



I=mT& T2 a T , 

 in which T represents the absolute temperature, m a constant 

 coefficient, b the number 0-9999938, a = 1-03550- 13 \, \ being 

 the wave-length in millimetres. 



In fact, if we apply this formula, first, to the platinum radiation, 

 we shall have : — 



* Comptes JRendus, xciii. pp. 146, 147 (1881). 

 Phil. Mag. S. 5. Vol. 13. No. 80/ March 1882. T 



