THE WINDS OF THE SOUTHERN HEMISPHEEE. 419' 



I do not take into this comparison the force of the N.E. trades on 

 a S.S.E. course (§ 813), because the vnnds along this route are 

 known not to be as steady as they are farther away from the 

 African coast. Thus it is clearly established that the S.E. trades 

 are stronger than the ^M.,and so tlieij should he if there he a 

 crossing of winds in the calm helt of Capricorn. 



816. The counter- trades of the southern hemisphere move, as 

 Ditto of the counter- beforo statcd, towards their pole more steadily and 

 tra^ies. briskly than do the counter-trades of the northern 



hemisphere. To give an idea of the difference of the strength of 

 these two winds, I cite the fact that vessels saihng through the 

 latter, as from New York to England, average 150 miles a day. 

 Along the corresponding latitudes through the former, as on a 

 voyage to Australia, the average speed is upwards of 200 miles a 



the following extracts of a letter, just received from that distinguished officer, 

 dated — 



"Frigate 'L'Alceste,' at Monte Video, May 10, 1860. 



" Dear Sik, — I am replying to your letter of the 30th of January last, which I 

 have received with the duplicates of that dated January 15th, 1859, which you have 

 had the goodness to send me through M. de Montholon, as well as the interesting 

 nautical monograph No. 1, and, finally, the manuscript j^assage from an article 

 relative to the force of the winds to the height and velocity of clouds and waves. 

 I regret exceedingly that I have not under my orders a squadi'on of sailing vessels 

 witii which I could put to sea, and devote myself to all these researches. _ Un- 

 fortunately, I have only steamers in my division, with the exception of the frigate 

 which carries my flag, "and political circumstances have retained me almost con- 

 stantly in the La Plata. I am now approaching the end of my command, and in 

 a few days must leave Monte Video to engage in some hydrographical works on 

 the coast of Brazil, and afterwards I shall return to France, where I expect to 

 arrive in the beginning of September. I shall not fail dming this voyage to make 

 a series of experiments such as you have indicated, in order to establish the rela- 

 tive force of the trade-winds in the southern and in the northern hemisphere- 

 determining the difierences of velocity of the frigate with wind aft and wind abeam. 



" In my last letter, of tlie 25th of January, I gave you the results obtamed by the 

 brig 'Zebra,' but they are very incomplete, and I wish, with the 'Alceste,' to 

 determine the comparative velocities obtained with a perfectly regular wind in the 

 difterent rates of going from the nearest the wind to wind full aft. It is evident 

 that the differences observed in this manner will be dependent on the special 

 qualities of each vessel used in the experiments, and that it will be also necessary 

 to take full account of the state of the sea ; but by multiplying experiments, one 

 will certainly arrive at an average in which confidence may be placed. I think 

 with you, that for a ship sailmg 6 knots, with wind fidl aft, there will be an 

 increase of speed of 2 . 5 to 3 knots, with the wind a little abaft the beam. I have 

 already had occasion to remark that for the ♦ Alceste ' this difference sometimes 

 exceeds 3 knots. My next letter will give you the details of the experiments which 

 I shall have made in this respect, Ixith south and north of the Line, which will 

 necessarily lengthen my voyage a little. I am too anxious to co-operate in my 

 feeble way in the great works you are carrying on, not to sacrifice willingly soma 

 hours daily whenever circumstances will permit." 



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