Essay on the Indian Summer. 145 



In confirmation, we may remark, that during the cold summer of 

 1816, when of course both these causes were acting with a diminish- 

 ed force, there was a very constant haziness of the air, so much so, 

 that the sun could be viewed with the naked eye until 9 or 10 o'clock 

 in the morning. A celebrated traveller in the south, relates a fact 

 which will convey some idea of the actual condition in which we 

 suppose the lower stratum of air to exist during the prevalence of 

 hazy weather ; he remarks " that over the ocean the sky exhibits a 

 paler blue than over the land ; when from the summit of the Andes 

 the eye is directed towards the great South Sea, a haziness uniform- 

 ly spread to about 10,000 feet in height is observed to cover as with 

 a thin veil the surface of the ocean — this appearance takes place in a 

 season when the atmosphere viewed from the coast, or at sea, ap- 

 pears pure, and transparent ; the existence of the opaque vapor is 

 announced only to mariners by the little intensity of the azure color 

 of the sky." Here it is evident that a slight additional density in 

 this lower stratum would intercept a large portion of solar light and 

 give a turbid or hazy appearance to the general atmosphere. 



By a very careful reference to Capt. Brantz' meteorological tables, 

 we find, that in a very few instances, he notes hazy weather coex- 

 isting with a northerly wind — this fact, however, does not militate 

 against the view we have offered, viz. that hazy weather is the result 

 of a southerly or easterly current, supervening to a cool northerly one 

 — for it is evident the same result would be produced if the differing 

 portions of air only come in contact — with this qualification, that the 

 superior dryness and force of a northerly wind, would give a much 

 shorter duration to the existence of haze — the continuance of which 

 would be incompatible with a dry westerly or northerly wind. 



We shall now proceed in a very general manner, to enquire, why 

 the Indian summer makes its appearance more particularly at the 

 close of autumn. This part of our subject, by no means void of diffi- 

 culty — appears capable of solution in the following manner. It is 

 well known that a constant and general wind prevails within the trop- 

 ics, moving round the earth from east to west, called the trade wind; 

 observation also confirms that without the tropics, both north and 

 south, the prevailing winds are westerly : the object of which ap- 

 pears to be a restoration of the equilibrium, which is disturbed by 

 the trade winds — this westerly or north westerly current, (for it would 

 be oblique in our parallel,) being often counteracted during the sum- 

 mer by opposite winds, [brought into existence by local causes — and 



Vol. XXVIL— No. 1. 13 



