40 Mayow 



spirit of nitre is expelled as by distillation, the alkaline 

 salt being left with the terra damnata in the ashes ; 

 and in proportion to the violence with which the 

 calcination is effected, in that proportion are the salts 

 alkalised when the nitrous spirit is expelled. Hence 

 we may gather that it is not advisable violently to 

 calcine diuretic salts (so named from promoting 

 urine), for, by doing so, those salts are deprived of 

 their nitrous and diuretic spirit. And hence it is 

 that the lye, say of the ashes of Genista^ is more 

 efficacious in dropsy than its fixed salt thoroughly 

 alkalised by violent calcination. 



The nitrous spirit of plants seems to be clearly 

 present in a fire of burning charcoal, for the smoke 

 from that fire assails the nostrils when brought near 

 to it, very much in th^ same way as the vapour that 

 proceeds from the spirit of nitre. And indeed it is 

 likely that the nitrous spirit which exhales from 

 burning charcoal in the form of smoke, is the reason 

 for that smoke being so acrid, and for its sometimes 

 causing suffocation. 



And further the nitrous spirit of plants manifests 

 itself strikingly in their fermenting juices, when these 

 have been kept for some time in a glass vessel care- 

 fully closed. For when these liquids are drunk the 

 nitrous particles irritate the nervous parts of the 

 throat with a quite striking pungency and bring on 

 an almost convulsive choking. So that, when liquids 

 of this sort are drunk, they are commonly and not 

 improperly said to cut. Moreover, the nitrous par- 

 ticles in which these liquids abound seem to be the 

 cause of their being so cold. For nitre mixed with 

 liquids makes them very cold, and almost freezes 

 them, as will be shown more fully elsewhere. 



In some plants the oily parts are so heavy and so 



