1864.] ^^'1 [Chase. 



feet, the heat-producing disturbance that is indicated by the barome- 

 ter, is represented by a lift of 15 lb. on each square inch to a height 

 of .00219x24000 ft. The quarter-daily disturbance from this 



. . „ 24000xl5x.00219 



cause IS, therefore, — r — — ^^.l"!*. 



770X.25 



It is more than likely that each of these results will require im- 

 portant modifications when the entire influence of the several con- 

 ditions of the problem is better understood. I have thought it 

 proper to pi-esent them in their present crudity, in order to show 

 the true points of departure, and to prepare the way for some further 

 considerations. 



Whatever other heat-disturbing causes there may be, there can be 

 little doubt that the three we have just been considering are the 

 most important. Dividing the astronomical day into four quadrants, 

 and representing the solar effect by S , rotation by R., and barometric 

 by B., it will be readily seen that the several positive and negative 

 influences must be distributed as follows : 



S. R. B. 



From Oh. to 6h. -f — — 



" 6h. to 12h. — — + 



" l'2h. to 18h. _ 4- _ 



" 18h. to Oh. -f + + 



The tables of average temperature at any given place would there- 

 fore furnish us with four equations for determining the value of each 

 of the disturbing elements, provided those that are unknown were so 

 insignificant as to be safely neglected. The eff"ects of these unknown 

 disturbances are confined within certain limits that can be pretty 

 satisfactorily determined. 



Our discussion of the barometric fluctuations demonstrated a ten- 

 dency of inertia to retard the efi'ects of rotation, so that the mean 

 daily altitudes are found nearer to Ih., 7h., 13h., and 19h., than to 

 Oh., 6h., I2h., and 18h. A like tendency is discernible in the 

 thermometer. 



There are three, and only three, quadrantal divisions of the day, 

 commencing respectively at Oh., at Ih., and at 2h., for which we 

 could obtain approximate positive values of S., R., and B. The 

 maximum solar efl"ect is deduced from the first, and the minimum 

 from the third of these divisions; while the maximum rotative and 

 barometric effects are exhibited in the third, and the minimum in 

 the first division. 



