(72) EFFECT OF THE SUN's BAYS. [aPP. n" III. 



No. III. b. 



NOTICE RESPECTING THE EFFECT OF THE SUN"'s RAYS, AJiD 

 THE DECREASE OF TEMPERATURE ON ASCENDING IN THE 

 ATMOSPHERE. 



In page 47- of this volume, a familiar approximation relating 

 to the effect of the sun's rays, during the summer solstice, in 

 the Arctic Regions, is given in a note. It may be worth while 

 to mention, that in an admirable article on " Climate," in the 

 third volume of the Supplement to the fourth and fifth edi- 

 tions of the Encyclopedia Britannica, this subject, together 

 with several others connected with atmospheric temperature 

 and pressure, is scientifically illustrated. 



The eflPect of elevation, in occasioning a reduction of tem- 

 perature, forms a part of the investigations in this article. 

 Instead of 90 yards of elevation producing a depression of 

 one degree of Fahrenheit in the lower atmosphere, as stated 

 by the late Professor Playfair in his " Outlines of Natural 

 Philosophy,"" and by other philosophers ; it would appear 

 from the author''s (Professor Leslie) researches, that the 

 height producing a change of a degree of temperature is 100 

 yards. In the higher regions of the atmosphere, a similar 

 change of temperature takes place, under a smaller difference 

 of altitude. Thus, in temperate climates, while the mean tem- 

 perature at the level of the sea decreases one degree of Fah- 

 renheit during an ascent of 300 feet above the surface, it suf- 

 fers a similar diminution in £95 feet, at the altitude of a mile ; 

 in 277 feet, at the height of 2 miles ; in 252 feet, at the height 

 of 3 miles ; in 223 feet, at the height of 4 miles ; and in 192 

 feet, at tlie elevation of 5 miles above the surface. In this 

 ratio, the decrease of temperature, on ascending a mile into 

 the atmosphere from the surface of the sea, would be about 

 17.7 degrees; on ascending two miles 36.1, three miles 55.9, 

 four miles 78.1, and five miles above the sea 103.5 degrees. 



