31 



northerly direction. It flows in a descending plane dif- 

 fering but slightly -from that of the limit of perpetual 

 snow. Its descent is known to be not far from 16,000 

 feet at the equator to very near the surface at the poles. 

 Over this country its range is from about 3,000 to 12,000 

 feet and vertically it cannot be far from 6,000 to 8,000 feet. 



It varies in direction and elevation with the changing 

 seasons runs lower in summer than winter and vary- 

 ing on different parallels, it flows near the earth when no 

 surface wind interferes. Over New England its course is 

 nearly W. S. W. to E. N. E., but west of the Alleghany 

 Mountains it is more southerly. Its elevation and direc- 

 tion also vary in the same latitude with the variations of 

 the weather, and probably correspond with the increase 

 and diminution of magnetic force. 



This is the counter-trade, and comes to us from the 

 South Atlantic Ocean. Within it form our storms. Its 

 ameliorating influences are seen in the southerly storms of 

 winter, in the gentle southwest gales of April and May. 

 Opposed to this is the dry, northwest wind which sweeps 

 down from the Arctic regions. Many maintain that this is 

 a surface wind. So it is when it has driven itself under 

 the counter-trade and fills the space between that higher 

 current and the earth. But it becomes an intermediate 

 one whenever an easterly wind prevails at the surface, and 

 its place is between the surface wind and the southwest- 

 erly upper current of the counter-trade. Our records 

 show that this frequently occurs. 



It is not necessary to enlarge upon this, as it is no part 

 of my purpose to combat theories, and I only allude to it 

 at all, that it might be seen clearly wherein Mount Wash- 

 ington, or any isolated peak, is superior to stations less 

 elevated, for the particular department of observations on 

 aerial currents. 



