172 Professor C. Piazzi Smyth's 



by Humboldt as precisely such localities, and vexed in the dry sea 

 son with constant whirlwinds which fill all the air with fine dust. 



The proof, therefore, that Lieut. Maury's theory of the trade - 

 winds, and with them the motions of the whole atmosphefe, is as 

 complete as can be expected at so early a stage of the discovery. 



His " wind and current charts," by which he appears to have 

 been led to an enlarged mode of treating the subject, seem to be 

 producing practical fruits also amongst navigators. On these charts 

 he has inserted by symbols, from all available American log-books, 

 the strength and direction of both wind and current each day. 

 Thence a glance will shew, by the accumulated experience of hun- 

 dreds of preceding voyages, what winds are likely to blow again on 

 any succeeding occasion. 



The individual symbols excessively multiplied in frequented parts 

 of the ocean, being found somev/hat puzzling, they are now being 

 condensed, and the combined results will be given for each four square 

 degrees of ocean in a wind-rose, or diagram of the points of the com- 

 pass, which will shew the whole number of observations discussed, 

 and the per centage proportion of each wind that blew. 



In their present form, however, they have produced sufficiently 

 marked results. 



Of the arrivals at San Francisco, the quickest passages have been 

 made by American vessels, and of these the six shortest have had 

 the wind and current charts on board. 



The average length of passage of all the American vessels through 

 the year is 188 days, while the average of the six shortest, who had 

 the assistance of the truly scientific principle of profiting by the ex- 

 perience of all their predecessors, was only 114 days! 



Again, these charts have indicated a much shorter passage 

 to the Line from the United States than vessels had been accus- 

 tomed to follow from time immemorial; and logs had just been re- 

 ceived of two vessels which had sailed at the same time, one a 

 merchant vessel, and the other a man-of-war, and possessing there- 

 fore, it is by courtesy to be supposed, superior sailing qualities; 

 yet by taking the old route, it had not reached the Line, when the 

 other had not only passed it, but was even 1500 miles beyond! 



The currents of the sea are receiving at the same timo much elu- 

 cidation, and an interesting system of cold currents from the polar 

 regions alternating with warm ones from the equator ; and again, un- 

 der currents, always existing, and generally flowing against the upper 

 one, and often with greater velocity, shew us that every part of the 

 navigable ocean is instinct with this sort of life ; and there is no 

 more possibility of finding a still and currentless part of the ocean, 

 than of discovering any part of a living human body where the blood 

 does not flow. 



When it is considered what a prolific source of shipwreck the cur- 

 rents of the ocean are, the importance of this elucidation of them 



