126 LIGHT SCIENCE FOR LEISURE HOURS. 



commends it favourably to consideration. But when 

 we examine it somewhat more closely, several very 

 decided flaws present themselves to our attention. 



Consider, in the first place, the enormous mass of 

 water moved by the supposed agency of the winds. 

 Air has a weight volume for volume which is less 

 than one eight-hundredth part of that of water. So 

 that, to create a water-current, an air-current more 

 than eight hundred times as large and of equal velocity 

 must expend the whole of its motion. Now the trade- 

 winds are gentle winds, their velocity scarcely exceed- 

 ing in general that of the more swiftly-moving portions 

 of the Gulf Stream. But even assigning to them a 

 velocity four times as great, we still want an air-current 

 two hundred times as large as the water-current. And 

 the former must give up the whole of its motion, which, 

 in the case of so elastic a substance as air, would hardly 

 happen, the upper air being unlikely to be much affected 

 by the motion of the lower. 



But this is far from being all. If the trade-winds 

 blew throughout the year, we might be disposed to 

 recognise their influence upon the Gulf Stream as a 

 paramount, if not the sole one. But this is not the 

 case. Captain Maury states that, ' With the view of 

 ascertaining the average number of days during the 

 year that the north-east trade-winds of the Atlantic 

 operate upon the currents between twenty-five degrees 

 north latitude and the equator, log-books containing no 

 less than 380,284 observations on the force and direction 

 of the wind in that ocean were examined. The data 



