54 Notices respecting New Books. 



or 



Tr[l+^7n?\/l-e' 2 ), 



if a = a(l+e) and /3 = «(1— e). 



On referring to Pontecoulant (vol. iv. p. 566), it will be seen 

 that the value of 1— c, which measures the rate of progression 

 of the moon's perigee, involves the terms 



-m 2 — g m¥ — ^ mW, 



which arc identical with the first three terms of the expansion 



of 5 m* VY^T. 



I will only add, that if the approximation be carried a step 

 further, the ratio of the apsidal angle to it will be found to be 



l-|.^( a + ^ v '^|l + l.^(a + /3)(25«H 5^/3 + 25^)1 



I am, Gentlemen, 



Your obedient Sen-ant, 

 Trinity College, Cambridge. A. TlIACKER. 



X. Notices respecting New Books. 



On the Atmospheric Changes which produce Bain and Wind, and the 

 Fluctuations of the Barometer. Second Edition, with additional 

 Essays and Diagrams. By Thomas Hopkins, M.B.M.S. London: 

 JohnWeale. 1854. 



r r*HE chief feature of Mr. Hopkins's Essay is the importance he 

 J- attaches to one fact, which he affirms has not hitherto been 

 sufficiently attended to ; and this is, the conveyance of heat to dif- 

 ferent regions of the earth's surface by vapour, and the eifects of 

 its liberation when the vapour is condensed. He denies tbe com- 

 petency of the commonly received theories of the trade-winds, &c, 

 and maintains that the principal cause of these and other similar 

 phenomena is to be found in the fact above mentioned. After 

 referring to the common theory of the trade- winds, originally ad- 

 vanced by Hadley, and now generally adopted, he says, " That the 

 effects of the unequal heating power of the sun on the surface of the 

 globe, and of the varying rotatory velocities of the different parts of 

 the earth between the equator and the poles, must be of the nature 

 described in this theory, is sufficiently evident. But it is not equally 

 evident that the causes pointed out are adequate to the production 

 of those general winds which are known to exist. The difference 



