Chase.] g^Q [March. 



loss that may arise from radiation into space, but it must modify 



the distribution of heat throughout the day in a manner that may be 



readily calculated. The available data are not sufficient to furnish 



us with complete results, but they give curious approximations that 



seem to open a wide field for profitable investigation. 



"Sir John Herschell finds the direct heating effect of a vertical 



sun at the sea level to be competent to melt .00754 of an inch of ice 



per minute, while according to M. Pouillet, the quantity is .00703 of 



an inr-h."* Taking the mean of these two estimates (.00728 in.), 



multiplying by the latent heat of water (142.6° F.), and dividing 



by the number of cubic inches in 1 lb. of water (28), we obtain 



.00728 X 142.6 no-n-r % f i , ■ a ■ . 

 = .Oo/Uib units 01 heat received per minute on 



28 



each square inch of the earth's surface that is exposed to a vertical 

 sun. The weight of the aerial column being 15 lb., and its ratio of 

 specific heat 25, the maximum effect of the direct solar rays is suf- 

 ficient to heat the whole atmosphere --^ — per minute, or 7.12° 



F. in 12 hours. 



Now, in consequence of the earth's rotation, the difference of 

 atmospheric "lift" between noon and midnight, is 182,886 ft. per 

 minute. The average difference for the twelve hours, is one-half as 

 great. " Rapid rotation, without friction or resistance, cannot in 

 itself alone be regarded as a cause of light and heat;"f but we have 

 found in our barometric investigations, that the ratio of the half- 

 daily velocity of rotation to that which would be conferred by twelve 

 hours' action of terrestrial gravity, is .00109, which maybe regarded 

 as the modulus of heat-producing resistance. If we multiply the 

 average difference of lift by the weight of the atmosphere, and by 

 the effective resistance, dividing the product by the ratio of specific 

 atmospheric heat, and the number of foot-pounds raised by a unit of 



, . 91108 X 15 X. 00109 .^,„^ , 



heat, we obtain — = < .74° i^ . as the amount of heat 



770 X. 25 



communicated to the air by rotation between midnight and noon, and 



abstracted between noon and midnight. 



The theoretical barometric lift is, as we have seen, .00219 of the 



entire weight of the atmosphere. Estimating the height of the 



aerial column when reduced to uniform surface density, at 24,000 



* Tyndal, Heat considered as a Mode of Motion. N. Y. edit. p. 431. 

 t Dr. J. R. Mayer. 



