332 ANNUAL OF SCIENTIFIC DISCOVERT. 



that it is only the lower portion of the atmosphere which is maintained 

 in this state of agitation ; that the upper portion may be perfectly 

 tranquil, and here the proportions of the two gases may change ; and 

 they may perhaps be disposed in separate strata in the order of their 

 specific gravities. He supposes that the cirri, the lightest of the clouds, 

 are formed in this lower portion of the atmosphere, near the boundary 

 which separates it from the upper and undisturbed portion ; while it is 

 in the upper portion of the atmosphere that shooting stars and auroras 

 appear. The upper portion he calls the stable atmosphere, and the 

 lower portion the unstable atmosphere. He conceives that by the 

 study of shooting stars we may ultimately arrive at a knowledge of 

 the composition of the stable part of the atmosphere. We observe 

 these meteors at elevations of 140 to 160 miles; they increase in 

 brightness as they approach the earth ; they disappear entirely as they 

 approach the lower part of the atmosphere, as if they entered a me- 

 dium which had not the elements necessary for their continued bril- 

 liancy. 



He questions whether the time of rotation of the still atmosphere is 

 the same as that of the earth ; and suggests that this circumstance 

 may perhaps explain the slow rotation of the magnetic poles of the 

 earth. 



As the editor of Sillimari's Journal has remarked, " physicists will be 

 slow to accept M. Quetelet's novel ideas on the constitution of the 

 atmosphere, unsupported as they are by experiment and in conflict 

 with long-established laws." 



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INFLUENCE OF TREES UPON TEMPERATURE. 



M. Becquerel has made in the Jardin des Plantes, with a sensitive 

 thermometer, certain observations at different hours of the day, by 

 comparison of which it was found that about 3 P.M., when the temper- 

 ature is highest, the difference sometimes amounted to 2 or 3 in fa- 

 vor of the atmosphere above the tree, whilst at sunrise, after a clear 

 night, the excess was on the other side, on account of the nocturnal 

 radiation. This experiment proves the cooling of trees and the at- 

 mosphere surrounding them under the influence of nocturnal radiation. 

 Vegetables near a wood are sooner affected by spring frosts and the 

 cold of autumn than vegetables at a distance from them. Under the 

 influence of solar radiation above the trees, there is a current of warm 

 air ascending during the night, and in the morning a current of cold 

 descends to cool the soil. When the sky is cloudy these differences of 

 temperature are very small. These experiments of M. Becquerel also 

 prove the correctness of the conclusions of Humboldt from the observa- 

 tions upon the temperatures observed at thirty-five stations in North 

 America, extending over 40 in longitude, namely, that the mean an- 

 nual temperature over this extent of country has not been sensibly 

 changed by the great destruction of wood which has taken place dur- 

 ing the time of the observations. 



THE WEATHER AND THE SCINTILLATION OF THE STARS. 



In a communication recently made to the Paris Academy of Sciences, 

 by M. Liandier, it is stated that the occurrence of storms and similar 



