707 



coast, for M. Horsburgh found at sea, in the 

 latitudes of India and China, an uninterrupted 

 barometric periodicity, at all seasons. It is, 

 above all, in studying the position of places, 

 where the deviations of the type are manifested, 

 that the cause which produces the regularity of 

 the atmospheric tides will be made clear. 



Since my departure from Lima, the professor 

 Don Hipolito Unanue, and the American Cap- 

 tain Samuel Curson, found, on the coast of 

 Peru and Chili, the same hours of the maximum 

 and minimum that are indicated in the preced- 

 ing tables (Vol. vi, p. 670) ; but M. Unanue 

 informs me, that " these hours appear to change 

 in ascending the Cordilleras of Peru ; and that 

 this delay, in the epoehas of the extreme 

 limits, appears to him to be owing to the winds 

 which blow differently on the coast of the Pa- 

 cific Ocean, and in the narrow vallies of the 

 Andes." I do not doubt the possibility of those 

 changes of epoehas ; but no naturalist has hi- 

 therto published a series of observations which 

 indicates them in a regular manner. The 

 question is, whether the winds and rains (as 

 during a part of the year at Bombay and Can- 

 ton), disarrange the movement of the barome- 

 ter, so that no type of regularity can be ascer- 

 tained; or, (which is very different) whether 

 places exist in the equatorial zone, where al- 

 ways, or at one season only, atmospheric tides 



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