THE TEADE WIND. 



129 



which is 29-968 inches for the former, and 30-023 inches for the latter, it 

 was inferred by Captain Maury that the greater pressure in the S.E. Trades 

 indicates a greater force and velocity* than the N.E. Trades. This, as 

 investigated by him, was confirmed by the daily rate of vessels passing 

 through them. He compared the sailings of 2,285 vessels, and found that 

 the homeward-bound vessels crossed the Trades of the North Atlantic 

 with the wind abeam at an average rate of 5-6 knots per hour, and across 

 the Trades of the South Atlantic at an average rate of 6 knots. As the 

 latter is with the wind generally dead aft, he argued that this rate would 

 be increased 2 or 2|- knots with the wind on the beam, and make the 

 difference still more evident. The comparative duration of each of these 

 winds in the Atlantic is thus given by Captain Maury : — 



(50.) The Force or Velocity of the Wind is an important element in 

 these calculations, and Captain Maury's system was enlarged upon by 

 Lieutenant J. C. de Brito, of the Portuguese Eoyal Navy, who investigated 

 the rates of sailing of 1,548 tracks across the Atlantic, and arrived at some 

 important and unexpected results, differing in some degree from the con- 

 clusions of the great American meteorologist. 



Lieutenant de Brito reduced the courses of all his ships to the most 

 favourable point of sailing for all ships, that is, with the wind free, and 

 took the months of February and March for one season, and those of 

 August and September for the opposite. His enquiries related to both 

 Trade Winds — the S.E. as well as the N.E. 



* It is generally argued, that less barometric pressure indicates increased force of wind, 

 and not the reverse, as it is here argued ; but from the following note it will be seen that 

 these pressures are more nearly alike than is stated above. 



t As this Table is founded on the assumption that the Equator is the division between 

 the two wind systems, instead of the parallels of 5° to 9° N., as is really the case, it 

 cannot be taken as a fair comparison of their relative duration. If the parallel of 5° N. 

 be taken as a division, the mean barometric pressure in the N.E. Trades is 30-057 inches, 

 and in the S.E. Trades 30-034 inches, naaking the latter the least. If the winds recorded 

 between 0° and 5° N. be added to the S.E. Trades, it will give a mean duration of 239 

 days, and make the N.E. Trades 172 days. 



N. A. 0. 



18 



