the Circulation of the Atmosphere, 361 



or south, is wholly hypothetical, and unsupported by any testi- 

 mony whatever. They may be there, or they may not ; it is im- 

 possible to say ; and we might with as much reason, as far as 

 evidence goes, assert the prevalence of furious hurricanes. 



The calms which have been named the calms of Cancer come 

 more directly within the limits of evidence, and the testimony of 

 thousands of seafaring men who cross the tropic every year can 

 readily be brought forward. Personal experience has, not un- 

 naturally, considerable influence on the judgment of an inquirer ; 

 and I may perhaps be excused if I quote from my own journal 

 that, in May 1856, H.M.S. l Calcutta' (a rather dull sailing 

 line-of-battle ship) ran from the Channel into the trades with a 

 fresh northerly wind the whole way. Between the latitudes of 

 45° N. and 25°. N she made never less, generally considerably 

 more, than 1 50' a day, a distance which was for her a very good 

 run. Our longitude was then, being outward bound, between 

 13° and 23° W. On the homeward passage, in July 1859, we 

 found calms and very light winds through nearly our whole course 

 from 30° N. 40° W. to 42° N. 32° W., and were a fortnight be- 

 tween these two positions. 



La Perouse, in August 1785, ran from Brest into the trade, 

 in longitude 16° W., without suffering from calms, and with a 

 prevailing wind from N.E. The expedition in search of La 

 Perouse, leaving Brest in the end of September 1791, found a 

 fresh north-easterly wind in latitude 46° N., longitude 8° W., 

 which carried them to Teneriffe, and thence into the trades in 

 longitude 17° or 18° W. 



Vancouver, under date April 1791, writes, " The wind, which 

 had been generally from the west, veered round by the north as 

 we advanced to the southward, and settled in the N.E. trade, ac- 

 companied with fine pleasant weather, which on the 26th, in lati- 

 tude 30° 54' N., afforded me an opportunity of obtaining several 

 sets of lunar distances their mean result showed the lon- 

 gitude to be 16° 21' 32"." (Voyages, vol. i. p. 8.) 



Cook's testimony is to the same effect. In 1772, he says, 

 "We left Madeira on the 1st of August and stood to the south- 

 ward, with a fine gale at N.E." And in 1776, " We passed Cape 

 Finisterre on the afternoon of the 24th [July] with a fine gale at 



N.N.E at four in the afternoon of the 31st we saw 



Teneriffe." 



And leaving on one side special instances, which may perhaps 

 be counted as exceptional, I would refer to the Tables of runs 

 and crossings from the Lizard to the Line, given by Maury 

 (Sailing Directions, vol. ii.), from which I have taken the fol- 

 lowing : — 



Phil. Mag. S. 4. Vol. 34. No. 231. Nov. 1867. 2 B 



