i()6 On the different GnfeS, 



breathing animals which breathe through real lunffs have 

 need of more air than thofe which merely evaporate, that is to 

 fay, than fiich was have no evident and real lungs ; and as, 

 in genernl, a ftronger fire requires a ftrongcr draught of air 

 than a weaker, in the like manner a more a6livc life requires 

 quicker breathing, and a more {]ua;gifli a (lower: as air afts 

 difierently on flame according as it is more or lefs clear, warm, 

 or dry, in the like manner it acls upon breathing and the 

 vital flame: and, iti the lafl: place, as flame burns more 

 brifl<ly according as it has free accefs to the air on all fides, 

 and is weaker when the air is withheld, and is at length to- 

 tally extinguiflicd, breathing is expofed to the fame effefts 

 under the like circum fiances. 



Tiiis Sylvius proved nothing by experiments, but he made 

 it probable, according to his manner, that fourilh particles 

 of nitre * floated about in the common atmofpbcre ; and 

 approached fo near to the prevailing principles of the prefent 

 day t, that he fuppofed fire (or caloric) was continually dif- 

 fufed through the air. 



The celebrated Spanifli mlneralogifi Alphonfo Barba was 

 acquainted with thofe pernicious damps v hich aril'e fo often 

 in mines, and which, though they refcmble air in other re- 

 fpefts, have however an offenfive fmcll, extinguifli lights, 

 and deprive men, birds, and even fnakes, of their life |. 



Boyle, to whom natural philofophy in general is under fo 

 many obligations, afcribed that incrcafe of weight which 

 metals accjuire by calcination §, as he had frequently obferved, 

 rather to the fire than to particles from the atmofphere, and 

 was therefore very remote from that opinion which prevails 

 in the prefent century, and which is fupjiorted by fo many 

 experiments; but he was at the fame time acquainted with 

 the carbonic acid gas as it riles from coral, when it cifcrvefces 

 with vinegar, from bread, cherries, grapes, pears, apricots, 

 plums, goofeberries^ peas, &c. when they ferment ||, and 

 its highly pernicious eflcfts on animals; as alfo with the in- 

 flammable, as it partly occurs in abundance in many mines, 

 for example, thofe of Hungary fl, partly as it arifes by a fo- 

 lution of iron in diluted fulphuric acid or muriatic acid **, 



■ Praxis Medicina;, lib. i. c. ii. § iii. 



-J- Ibid. lib. iii. cm. § 47. 



+ Bergbiichlein, FVankf. 1716. part i. c, 2. p. 5 — 8. 



§ Dctcft. penetrabilit. vitr. p. 296, 297. 



Il Second continuation of Phyfico-meclianical Experiments, art. ii. 

 exp. II. art. iii. cxp. i. 7. 10, 11. art. v. «xp. i, 2. 13. 



fl Examinat. of Antipuriftahs, Optr. b. ii. p. ^66. 



■'"■ Nova Exper mcnra Phyfico-mechanica de Vi Aeris ela-ftica, p. 152— 

 154: New Experiments touching the Relation betwixt Flame an J Air, 

 Opcr. b. iii. p. 255, 256. 



and 



