687 



introduction of a memoir somewhat rare, and 

 which bears the title of Observaciones meteoro- 

 logicas de los ultimos nueve meses de el am, 

 1769. The horary observations made at Mex- 

 ico were at first regarded by Cotte, as owing to 

 the imperfection of the instruments ; but, from 

 the year 1784, consequently long before he 

 could have any knowledge of the labors of La- 

 manon, he recognized * his first error, in attri- 

 buting the phenomenon " which he thinks he 

 observed in Europe, to a cause which has some 

 relation to the atmospheric tides occasioned 

 by the moon." 



Neither the observations of Thibault de 

 Chanvalon (1751), nor the small number pub- 

 lished by Alzate (1769) corresponded to the 

 tropical hours, that is, to the epochas when the 

 barometer arrives at the convex, or concave 

 summits of the curve of its diurnal variations ; 

 in the voyage of Le Perouse, MM. Lam anon 

 and Monzes made the first continued observa- 

 tions in 1785, from hour to hour, during three 

 days and three nights. They were then in the 

 middle of the Atlantic Ocean, between the pa- 

 rallels of 1° nor. lat. and 1° south lat. -f- 



The labors of Lam anon are eight years ante- 

 rior to those which were undertaken at Calcutta 



* Memoirs of Meteorology, Tom. ii, p. 304. 



t Voyage de la Perouse, 1797, Tom. iv, p. 257, 264. 



