GEOGRAPHY AND ANTIQUITIES. 323 



"In connection with the interesting subject of the geography 

 of the ocean, I may call your attention to a little work of great 

 merit, which has lately appeared under the title of * Physical 

 Geography, in its Relation to the prevailing Winds and Currents,' 

 by Mr. J. K. Laughton. A perusal of this book will show how 

 wide is the field embraced by this important branch of geographi- 

 cal science, and at the same time how much yet remains to be done 

 before we attain to a satisfactory knowledge of those great move- 

 ments of the ocean and atmosphere included under the terms 

 gulf-stream, equatorial current, trade-winds, monsoons, and so 

 forth. Mr. Laughton, in the book to which I allude, has called 

 in question the accuracy of the prevailing theories intended to ex- 

 plain these grand and, in some respects, complex phenomena. 

 The received hypothesis with regard to the trade-winds, for ex- 

 ample, first outlined by Halley towards the end of the seventeenth 

 century, but developed by Hadley about 50 years later, and 

 modified a few years ago by Maury, he shows to be quite inade- 

 quate to explain all the facts of the case. This hypothesis, as is 

 well known, assumes that the lower strata of the atmosphere near 

 the equator, being overheated by the sun's rays, expand and rise 

 into the upper regions of the aerial envelope, their place being 

 taken by a cooler air, which rushes from the higher latitudes of 

 the north or south as the case may be ; and, moreover, that the 

 ascending heated air travels backwards, as an upper current, to 

 the latitudes where the cool wind originates, and then, descend- 

 ing again, the aerial circulation is completed. One of the most 

 striking objections made by Mr. Laughton to this explanation is 

 that the equatorial zone is far from being the hottest part of tropi- 

 cal and subtropical regions. He shows, as a matter of fact, in the 

 North Atlantic basin, that the Great Desert of Sahara has a tem- 

 perature from 20 to 50 degrees hotter than the equatorial zone ; 

 yet, so far from a cool current of air being drawn in from the At- 

 lantic towards this heated region, the north-east trades pass 

 straight onward in their southerly course without the slightest 

 indraught towards the African coast. He also shows that there is 

 no proof of a vertical movement of the air at the equator, or in 

 the latitudes where the upper currents are supposed to descend 

 again. A multitude of similar or parallel instances are adduced 

 from other parts of the earth ; in fact, nothing has more surprised 

 me, in perusing the work, than the great amount of reading and 

 research the author has applied to the elucidation of this and kin- 

 dred problems. Having shown the untenability of the received 

 hypothesis, he modestly advances a new one of his own. This is 

 difficult, perhaps, to explain in a brief manner. But he shows, 

 from the most varied evidence, that the general movement of the 

 atmosphere over the whole earth is from west to east; and that 

 in regions where the prevailing winds at the earth's surface are 

 not westerly, an upper and strong westerly movement exists above 

 the lower winds. The trade-winds, monsoons, and all other par- 

 tial atmospheric movements he shows to be chiefly eddies and re- 

 flected currents of greater or less constancy ; and he confirms this 



