Notices respecting Neiv Books. 55 



in the rotatory velocities of different latitudes must certainly have 

 the kind of effect described upon any winds which pass from the 

 equator to the poles, and from the poles to the equator ; and the 

 degree of effect will be proportioned to the rapidity of the passage 

 of the wind from one latitude to another. But the unequal heating 

 of the surface of the globe, and consequently of the air near it, by 

 the sun, does not, as will be hereafter shown more fully, produce 

 those palpable or strong winds which blow in some parts towards, 

 and in other parts from, the tropics. The heating of the surface of 

 the globe and of the air near it, by the sun, is not a sufficiently pow- 

 erful cause to produce these winds, though, like the law of diffu- 

 sion, such surface-heating may, and no doubt does, to a certain 

 extent, bring into active operation another and a more powerful cause, 

 and as we shall see hereafter, one that is fully adequate to their 

 production." This other " and more powerful cause " is the heat 

 taken up in the process of evaporation, and after being carried away 

 to other regions, liberated on the condensation of this vapour. " In 

 the following pages," says the author, " it is proposed to show that 

 the heat which is thus taken up by vapour, in the process of evapo- 

 ration, is carried away to various parts of the atmospheric regions, 

 and in those parts is liberated on the vapour being condensed ; and 

 that it is this liberated heat which produces that inequality of tem- 

 perature which causes the greater part of those aerial movements 

 called winds on different parts of the surface of the globe." (P. 6.) 



On a subject so intricate, and of which so little is known as the 

 present one, it is dangerous to make any positive assertions involving 

 the general laws of the phenomena. And still more dangerous is it 

 to assert that certain causes are, or are not, sufficient to account for 

 certain effects, whilst neither the causes nor the effects have yet 

 been submitted to accurate measurement and calculation. We agree 

 with Mr. Hopkins in thinking the common theory of the trade- 

 winds unsatisfactory in some respects ; and for this very reason, 

 viz. that we possess no accurate estimates of the elements involved 

 in the problem. Mr. Hopkins asserts, that, "if no other cause of 

 rain or wind existed than those yet named " (viz. in the ordinary 

 theories), " there would be no copious rain nor strong wind in any 

 part of the world, as those causes would evidently all operate mildly 

 and gently. Inequality of temperature, on different parts of the 

 earth's surface, in no place directly produces a strong wind, though 

 there are parts where that inequality is great within small di- 

 stances." (P. 11.) Now here, we think, Mr. Hopkins has made an 

 assertion difficult of proof; and, further, that his own theory is open 

 to the very same objection, viz. that the action of the heat of vapours, 

 pointed out by him as the most powerful cause of winds, &c, would 

 seem at first sight to be just as likely to " operate mildly and gently" 

 as the inequalities of temperature, &c. 



His reasonings from page 14 to page 18 are rather obscure, and, 

 as relating to operations of which we have little or no experimental 

 knowledge, cannot be considered satisfactory ; and as these pages 

 appear to contain the main part of our author's theories, we fear that 



