1821.] Causes of Calorific Capacity, Latent Heat, %c. 379 



of oxygen to nitrogen in a given portion of atmosphere, whether 

 it be taken within doors or without, from the cabins of sickness, 

 or the mansions of health, from the highest regions of the. air or 

 the surface of the earth, from the sea or the land, from the torrid 

 or the frigid zone. If this be the case, it cannot, therefore, be to 

 any excess or defect of oxygen that the salubrity or insalubrity 

 of the atmosphere in some places is owing. Does not the 

 healthiness or unhealthiness of the air depend on its absolute and 

 not comparative quantity of humidity? Granting such to be the 

 case, we should say that high and elevated regions are more 

 healthy than low ones ; dry absorbent soils, as limy and chalky, 

 than clay and marshy ; dry and cold climes, than warm and damp 

 ones. And in the same place, we should say the morning air 

 after a copious deposition of dew is more healthy than the even- 

 ing, when the dew is beginning to precipitate ; the winter more 

 healthy than the summer ; a cold dry atmosphere more healthy 

 than a warm close one ; a windy agitated air, which carries oft', 

 and thus prevents from being inhaled, the continual exhalations 

 from the body, more conducive to health than a quiet still one. 

 We should likewise say, that large confined towns in which the 

 air is generally warmer, more quiet, and more humid, from the 

 continual culinary operations, and the great quantity of animal 

 exhalations, are much more insalubrious than open country 

 situations ; where there is not that immense collection of animal 

 matter; where the cold is commonly greater; where no artificial 

 heats are kept up ; where humidity following the ordinary laws of 

 nature can be deposited, and thus, for some hours at least, render 

 the atmosphere more dry and more pure ; where the winds can 

 blow with unrestrained freedom ; and where the air, if I may so 

 express myself, has room to be purged and to be purified. Now 

 the truth is, that all these conclusions are known to be correct. 

 Dry soils and high situations have always been preferred for 

 health. Damp low islands where fogs prevail are usually allowed 

 to be pernicious. The morning air has been always considered 

 one of the greatest promoters of health ; which has received a 

 beautiful illustration from some researches of one of our judges, 

 who found that out of 800 individuals that had attained an 

 extended age, their habits agreed in one point only, early rising. 

 A brushing cold day is generally conceived more healthy than a 

 warm muggy one ; and the country is ever allowed more salu- 

 brious than the city. In those climes, as in Abyssinia, &.c. 

 where the lains last for a considerable period, the sickly seasons 

 commence and terminate with the rains. Even a lime kiln, I 

 have beeo informed, contributes to the healthiness of the neigh- 

 bourhood. This probably depends chiefly on the desiccative 

 property of the lime absorbing and condensing within itself the 

 vapoui- ofthe atmosphere, thoughlime indeed has another property 

 not less salubrious, when exposed to the air, that of absorbing 

 carbonic acid gas ; but the beneficial effects of this are, perhaps, 



