Temperature (jftke Lower Strata of the Atmosphere. 355 



The author discusses these four questions successively, and 

 gives an account of his various observations, which were all 

 made during the year 1837 and the two first months of the pre- 

 sent year. The results obtained have led to the following con- 

 clusions : 



1^^, The increase of temperature as you ascend, which is 

 most conspicuous at the setting of the sun, however variable it 

 may be, whether as regards its intensity, or its limit of elevation, 

 is a constant phenomenon, whatever may be the condition of 

 the sky ; with the single exception of violent winds.* 



2c?, The period of the maximum of this increase is that im- 

 mediately following the setting of the sun. Starting from this 

 » time it remains stationary, or even frequently diminishes, es- 

 pecially when the dew is abundant.f At the time of sunrise, 

 the increase is most frequently less than it was at sunset. 



3J, The limit of elevation to which the increase of tempera- 

 ture extends, appears rarely to surpass the height of 100 feet, 

 even when the sky is perfectly clear and serene. When it is 

 very cloudy, and especially in winter, this limit is much lower 



Athy The increase of temperature in ascending, varies, both 

 according to its intensity and as to the limits of its elevation, 

 according to the different seasons of the year. It is especially 

 during the winter, and when the surface is covered with snow, 

 that this phenomenon presents the most remarkable results. 



The extraordinary severity of the last winter, enabled the 

 author to make many observations, upon the remarkable diffe- 

 rence which may exist between the temperature of different 

 strata of the air but little separated from each other. The 

 maximum of this difference amounted, on the 20th of January, 



* The author establishes by a great number of observations, that the 

 plionomenon is not confined to those occasions in which the sky is clear and 

 serene, as had hitherto been supposed. It also exists, though in a less de- 

 gree, even when the sky is overcast ; excepting always the periods of violent 

 winds. 



t The author has almost constantly observed that an abundant descent 

 of dew has a tendency to raise the heat of the strata of air which are 

 nearest to the earth, and, consequently, to re-establish, to a certain point| 

 an equilibrium between these strata and the superior ones. 



