570 PHILOSOPHICAL TRANSACTIONS. [aNNO 1779. 



ing, arising from those changes of the salubrity of the atmospherical air; and he 

 was informed, that no particular diseases appeared which could indicate any re- 

 markable change of air. 



Nature is not so partial as is commonly believed. She has not only given us 

 an air almost equally good every where and at every time, but has allowed us a 

 certain latitude or a power of living and being in health in qualities of air which 

 differ to a certain degree. By this he did not mean to fleny the existence of cer- 

 tain kinds of noxious air in some particular places; but only meant, that in ge- 

 neral the air is good every where, and that the small differences are not to be 

 feared so much as some people would make us believe. Nor did he mean to 

 speak here of those vapours and other bodies which are accidentally joined to the 

 common air in particular places, but do not change its nature and intrinsic pro- 

 perty. This state of the air cannot be known by the test of nitrous air, and 

 those vapours are to be considered in the same manner as we should consider so 

 many particles of arsenic swimming in the atmosphere. In this case it is the 

 arsenic, and not the degenerated air, that would kill the animals who ventured 

 to breathe it. 



In this place therefore he did not mean to speak of those changes which do 

 not immediately alter the nature of the air itself. The other states of that fluid 

 are of another kind, and they are not to be examined by means of nitrous or in- 

 flammable air, the uses of which last, he means to show on another occasion. 

 The same thing may be said of those vapours or particles which may be good for 

 respiration, and do not change the nature of the air. Some vegetables, for in- 

 stance, can diffuse through the air such exhalations as may be of real use to the 

 animal economy, when they are breathed for a long time, or imbibed by the 

 pores of the skin. He remembered to have often put various flowers, as roses, 

 pinks, &c. in vessels full of common air confined by quicksilver, where he left 

 them for several hours; after which time he found, that the air was not at all 

 altered, but that various animals seemed to breathe it very well, notwithstanding 

 the flowers had filled the greatest part of the vessels. On the contrary, he had 

 found, that the vapours arising from lime slacked in water, either do not alter 

 the air at all, or very little ; though when breathed with the air, they occasion 

 the death of animals. 



He would not have any one suppose, that bethought it of little importance to 

 know the goodness of the atmospherical air, and the changes it undergoes. On 

 the contrary, he believed it to be a very useful inquiry for mankind, because we 

 do not yet know how far one kind of air more than another may contribute to a 

 perfect state of health ; nor at what time small differences may become very con- 

 siderable, when one continues to breathe the same kind of air for whole years, 

 especially in some kind of diseases. An exact method of examining the good- 



