1870.] Meteorology. 549 



currents, causing 'friction ' and ' lightning] the sudden shock of the 

 impenetrable masses the ' thunder! *** 



" Regarding our atmosphere as a homogeneous metallic body."! 



Our readers will be ready to admit that Capt. Maury has not 

 much to fear from opponents like Mr. Armit. 



We are glad, however, to be able to record a contribution to 

 theoretical meteorology of a character very different to the foregoing. 

 This is c Physical Geography in its relation to the Prevailing Winds 

 and Currents,' by Mr. J. Knox Laughton. We regret that we can 

 only very briefly allude to its contents. Mr. Laughton gives a 

 concise account of the existing winds, and then discusses the accepted 

 theories of the origin of the great currents of air and water which 

 exist on the globe. He shows that Hadley's theory of the trade 

 winds, as developed by Dove, is insufficient to explain the facts 

 observed. The air does not flow towards the region of highest 

 temperature for the time being. In the old continent this district 

 is the north of Africa and Arabia, towards which the trade wind 

 does not blow. Secondly, he concludes that the rotation of the 

 earth does not materially affect the direction of the currents of air, 

 because " the friction between the air and earth is so great, that the 

 air almost instantaneously acquires the velocity of the points of 

 the earth to which it is transplanted," and because Dove's theory 

 will not explain due easterly or westerly winds any more than 

 north-westerly or south-easterly winds in the northern hemisphere 

 (S.W. or N.E. in the southern). The laws of motion of flowing 

 water are next described, and the action of obstacles in altering 

 the direction of the current, and producing reverse currents or 

 backtvaters. After giving an account of the currents of the sea, 

 similar to that previously given of the winds, the author concludes 

 " that wind, acting not only on the surface of the sea, but, by means 

 of intense friction, to a considerable depth, is the chief " — he will 

 not say the only — " cause of the numerous oceanic currents." 



The final theory which Mr. Laughton adopts is thus stated : — 

 "The whole atmosphere, relatively to the surface of the earth, 

 continually moves, or tends to move from west to east ; and the 

 prevalent local variations from that direction are either eddies, or 

 deflections, formed in accordance with the principles which regulate 

 the motion of fluids." 



Our space will not allow of our criticizing Mr. Laughton's 

 reasoning in detail, but we cannot omit to give him credit for 

 having collected a most valuable series of facts from the most 

 authentic and most recent sources, and discussed them with thorough 

 conscientiousness. Although we may not agree with all his conclu- 

 sions, we feel that he has produced a very useful and interesting work. 



* P. 68. f P. 112. 



