of the Lower Strata of the Atmosphere. 37 
the conducting power, which is pretty considerable, of the ma- 
terials which compose the edifice, must have tended to retard 
the cooling of the surface by the effects of nocturnal radiation. 
From this it follows that the increase of the temperature of 
the atmosphere upwards, might often have appeared more con- 
siderable than it really was. In these various respects, the ob- 
servations of Six, however interesting they may have been at 
the time when they were made, do not possess a sufliciently 
exact character, to be of much avail in the present state of the 
science.* 
Another motive which induced me to undertake new re- 
searches on the variations which take place in the temperature 
of the lower beds of the atmosphere, is the connection now 
well known to exist between that temperature and the radia- 
tion of the earth. The discovery of the Ethrioscope by Leslie, 
which measures the intensity of this radiation, furnishes the 
means of studying these two facts simultaneously, and of en- 
quiring in what degree they influence each other. The hy- 
grometrical state of the air must also exercise a certain influ- 
ence, particularly in the evening, on the temperature of the 
lower beds of the atmosphere: we know, in fact, that the de- 
position of dew is constantly followed by an elevation of tem- 
perature ;f therefore, all things being equal in other respects, 
the cooling of the lower strata of the atmosphere must be in 
the inverse ratio of the degree of the saturation of the air ; or, 
in other words, of the quantity of dew ready to be deposited. 
For the purpose of prosecuting these enquiries, I procured 
amast or pole 114 feet long, composed of two pieces of fir 
securely bound to each other. After having succeeded, not 
* The same thing may be affirmed of White of Selbourne’s observations, 
in which he compares the temperature of the plain with that of the summit 
of a neighbouring hill. It may be conceived to what a degree the tempera- 
ture of the air in each of these stations might have been influenced either 
by neighbouring objects, or even by the character of the ground. Moreover, 
White expresses himself with little precision on many essential circum- 
stances. 
t See my observations on this subject in the 34th Number, p. 353 of the 
Bibliotheque Universlle (New Series.) 
