Intelligence and Miscellaneous Articles. 245 



the mean temperature is different. We see from this the difficulties 

 in the exact determination of the temperature of a place, which is 

 one of the elements taken into account in classifying climates. 



In his memoir, M. Becquerel gives all the mean temperatures at 

 6 and 9 o'clock in the morning, 3 and 9 in the evening, at 1*33 metre 

 at the north, and at midday, at 16 metres and at 21 metres above 

 the soil, from the 1st of June 1860 to the 1st of June 1862, and the 

 differences between these temperatures, as well as the mean tempe- 

 rature and those of the seasons. The discussion of the results ob- 

 tained by comparing the observations made in this memoir leads to 

 the following consequences. 



The solar radiation increases the temperature of the air exposed to 

 its action, an effect which does not take place in the north, where 

 the instruments are protected from this action. This effect is 

 independent of the terrestrial action when the soil has been heated. 



The increase of temperature with the height, up to 21 metres, is 

 put in evidence in the Tables of observation. 



It is difficult to admit that the temperature of the air observed at 

 the north, as usually done, exactly represents the temperature of the 

 air resulting from the mixture of layers of air not having the same 

 temperature. 



The terrestrial radiation, according as the soil has been heated by 

 the solar action or cooled by the celestial radiation, doubtless exer- 

 cises a great influence on the temperature of the air, to a height which 

 depends on the nature of the soil and of that of the bodies which 

 cover it, an influence which has hitherto been too much neglected in 

 observations on the temperature of the air ; but it is necessary to 

 take into account the direct action of the sun on the air, which pos- 

 sesses, in fact, a feeble absorbing power that increases with its den- 

 sity in approaching the soil. — Comptes Rendus, June 22, 1862. 



RESEARCHES ON THE REFRACTIVE INDICES OF BODIES WHICH 

 ONLY ASSUME THE GASEOUS CONDITION AT HIGH TEMPERA- 

 TURES. ABNORMAL DISPERSION OF IODINE VAPOUR. BY M. 

 F.-P. LEROUX. 



The kindness with which the Academy has received my first 

 attempts* to study the refraction produced by gaseous media, has 

 encouraged me to continue these researches in spite of the numerous 

 experimental difficulties which they present. I have proposed not 

 only to extend them to a larger number of substances, but also to 

 study the dispersion produced by gaseous media. 



In the present communication I draw the attention of the Academy 

 to the dispersion produced by iodine vapour. This body deserves, 

 in fact, special mention, both from the difficulties of observation of 

 all kinds which it offers, and from the novelty of the phenomenon to 

 which it gives rise. 



* Phil. Mag. vol. xxi. p. 296. 



