in their relation to the Seasons. 241 



logons to that which a tone determines on the special sensi- 

 bility of hearing. 



Cassini, on his part, attempted to shew to what degrees of 

 the thermometer, at Paris, the different sensations of a mode- 

 rate, a strong, and an excessive heat correspond. 



Finally, Jerome de Lalande has proposed a thermometer 

 graduated precisely according to the relations which exist be- 

 tween the habitual movements of the external temperature, and 

 the modifications of the animal sensibility. 



Every one knows the numerous and minute meteorological 

 observations collected with no less perseverance than exacti- 

 tude by astronomers on many points of the globe. These 

 tables, every day more substantial, and which attest at once 

 the persevering zeal and varied knowledge of the superior men 

 who drew them up, cannot be too much multiplied. It is on 

 them that the future success of meteorological science rests. 



M. Fuster, on entering upon the first part of his subject, 

 has skilfully availed himself of the labours we have just allud- 

 ed to. He has joined to them many experiments of his own, 

 and which have for their special object the research of the ac- 

 tion of the physical qualities of the air on man, and in a word, 

 the study of the organic action of the seasons. 



The physical qualities of the atmosphere, and temperature 

 at their head, undoubtedly play the first and principal part iu 

 the pathogenic influence of the seasons. But we ought to dis- 

 tinguish well in this arduous question, absolute from sensible 

 heat. Absolute heat is that whose intensity is measured by 

 the rise of the liquid in the thermometer ; sensible heat, 

 on the other hand, is estimated by the impression produced on 

 our organs. Now, the effect of sensible heat is not always 

 j)roportional to the degi-ee of absolute heat. Considerations 

 borrowed, some from meteorology, others from the organism, 

 explahi this difference. Thus, independently of all variation 

 of absolute temperature, atmospheric electricity, the dryness 

 or humidity, the tranquillity or agitation, of the air, — conside- 

 rations drawn from meteorology ; and different anatomical, 

 physiological, and vital modifications, such as cutaneous tran- 

 spiration, innervation, — considerations borrowed from Ihe or- 

 ganism, cause the sensible heat to vary much. 



