WAVES IN THE AIR. 179 



wave is at its highest point in our country, is 

 precisely that given by American travellers, for 

 the occurrence of that most remarkable me- 

 teorological phenomenon the Indian Summer. 

 In America, at this period, generally from the 

 12th to the 17th of November, after a foretaste 

 of the severities of winter has been felt, a 

 sudden change of temperature takes place, a 

 delicious warmth is felt, the sky is without a 

 cloud, not a breath of air is stirring, and the 

 whole atmosphere is filled with a glowing trans- 

 parent haze. In three days this is all gone, 

 and winter comes on quickly afterwards. In 

 Switzerland, the same phenomenon has been 

 remarked from time immemorial. About the 

 llth of this month, the fete of St. Martin is 

 celebrated, and the inhabitants call the delightful 

 four or five days' return of summer weather at 

 that time, after, to all appearance, the summer 

 has ended, TEte de St. Martin, or St. Martin's 

 summer. Whether these interesting facts are 

 more than mere coincidences, whether the 

 great wave has anything to do with them or 

 not, it is not at present possible to ascertain. 



Some curiosity will, doubtless, be felt to 

 know how, seeing that the phenomenon cannot 

 be rendered visible to our eyes, its existence 

 has been ascertained. It is true, we cannot see 

 this wave, but its presence may be felt by 



