706 



to regularity is observed, whenever, even for 

 some hours only, the weather begins to grow 

 clear. In the same season, and in the same 

 latitude, the atmospheric tides are very sensible 

 in the open sea, while the periodicity disappears 

 on the coast *. M. Horsburgh also observed, 

 that the high lands that bound the strait of 

 Sincapore (a pass of small breadth) suffice to 

 mark the regularity of the horary variations. 



It may appear surprising that at the foot of 

 the Cordilleras of Venezuela, New Granada, 

 Quito, and Mexico (at Cumana, La Guayra, 

 Calabozo, Guayaquil, Payta, Lima, and Vera 

 Cruz), the variations attain their extreme limits 

 at the same hours as in the high vallies and 

 table-lands of Caraccas, Santa Fe de Bogota, 

 and Popayan (between 500 and 1400 toises) ; 

 while in India the configuration of the lands 

 modify in a very striking manner the phenome- 

 non of the atmospheric tides. This difference 

 between America and a small part of equinoxial 

 Asia, appears to arise from climateric circum- 

 stances ; almost every where between the tro- 

 pics, the same wind (E.N.E. or E.S.E.) brings 

 layers of air of the same temperature ; but in 

 India, the variable monsoons occasion extraor- 

 dinary gusts against the elevated parts of the 

 land. Their effects are not felt far from the 



* Nicholson's Journ., Vol. xiii, p. 20. 



