688 



by MM. Trail, Farquhar, Pearce, and Balfour % 

 but as the results of the latter were iriserted in 

 the fourth volume of the Asiatic Researches, 

 published at Calcutta in 1795, while the voyage 

 of the unfortunate Perouse appeared only in 

 1 797, the observations of India acquired more 

 celebrity in Europe ; and from them, at my 

 departure for America, I learnt the regu- 

 larity of the horary movements of the baro- 

 meter. Ideas too systematic on the periodicity 

 of all the maladies in the torrid zone, and on 

 the influence of the moon on the vital move- 

 ments, had fixed the attention of some English 

 physicians in the West Indies and at Calcutta, 

 on the variations of the weight of the atmos- 

 phere. Doctor Moseley* speaks of horary 

 changes, in his Treatise on Tropical Diseases 

 (1792, p. 3, 550, and 556), and Doctor Balfour, 

 who had not less faith in lunar and solar in- 



* " The barometer/' says Moseley, <e presents a phenome- 

 non^ the English West India Islands, and other regions of the 

 tropics, which is not yet verified in the temperate zone ; the 

 mercury has two movements by day ; one of descent, the 

 other of ascension ; they correspond to the diurnal progress 

 of the sun. The mercury mounts as the sun approaches the 

 zenith and the nadir, and descends as the sun recedes from 

 those points." This coincidence is not rigorously true. 

 The author might have observed that the maxima precede 

 the passage of the sun by the zenith and the nadir, from one 

 to three hours, and that the minima succeed that passage an 

 equal number of hours. 



