93 



from eighty-eight to ninety-two degrees. Tiie 

 extremes were eighty-three and ninety-seven de- 

 grees, which is conformable to my observations. 

 It is true, that, from the curious researches of 

 Mr. Gay-Lussac, the hygrometer can never in- 

 dicate beyond ninety degrees in air in contact 

 with a saturated solution of muriat of soda ; but 

 the water of the sea is every where so distant 

 from the point of saturation, that the salt which 

 it contains would scarcely change a single de- 

 gree the point of the greatest humidity, that the 

 lower strata of the air in the basin of the seas 

 might attain. This point would be indicated by 

 the hygrometer, if the tranquillity of the atmos- 

 phere were not troubled by currents. 



The wind, in displacing the particles of the 

 air, does not make the hair rise to dry, as it 

 causes the descent of a thermometer exposed to 

 the sun by carrying off the strata of air strongly 

 heated. Numerous experiments % of Mr. de 

 Saussure prove, that the air acts in the same 

 manner on hygroscopic substances, whether it 

 be in motion or at rest ; consequently the in- 

 fluence of horizontal or descending winds be- 

 comes sensible to the hygrometer inasmuch only 

 as these winds bring strata of air less loaded 

 with vapors. If oblique currents are establish- 

 ed, either by a sudden acceleration in the decre- 



* Essai sur PHygrom€trie, § 150—156, 



2 c 2 



