On Dr. MUchlU's Theory, ^c. 133 



fepton, and none others, were known to afford peftilential 

 air The fame rule applied to vegetable produflions, of what- 

 ever kind they might be. On this occafion it was exhibited 

 in evidence, that the perfons who were engaged ftead.ly 

 among the ajhes, foap, and fat of thofe manufaaones were 

 protected as it were from peftilential difcafes, and fared 

 mightily better than their neighbours. 



A part of this doftriue foon after received confirmation 

 from Count Berchtold's and Conful Baldwin's account of 

 the beneficial effeds of oil in keeping off and relieving the 

 fyntptoms of the plague in Afia, and.from the remarkable ex- 

 emption of the Nantucket whalemen from malignant fevers 

 on their long voyages over every part of the ocean. 



From the funey of the faels relative to alkahs and oih, 

 there could hardly remain a doubt that they aaed upon the 

 acid of p.fileucc, by neutralizing or decompounding it : ftill, 

 if this acid confined of fepton and oxygene chemically united 

 during the putretaaion of organized bodies, why did not 

 thofe elementary fubftunces, it was alTced, which conftitute 

 the bafes of azotic and vital airs refpeaively, incorporate in 

 the atmofphere, where they exift in ftates apparently very 

 favourable to combination? The rcafon appears to be, tliat 

 after fepton and oxygene, in their feparatc forms, have con-^ 

 neaed themfelves with caloric enough to form diftina gafes, 

 they are repelled thereby to dlftances greater than chemical 

 attraaion can reach, and therefore remain feparate. This 

 idea, which Dr. Mitchill originally ftavted, has fincc been 

 confirmed by Citizen Guyton's account of the poiTibility 

 of bringing the bafes of the two airs into chemical union, 

 by coin°prefling them with a force equal to feveral atmo- 

 fphcres; a part of the caloric in fuch cales, according to Dr. 

 Darwin's idea, being crowded out after being compelled 

 to quit its hold. Indeed it fcemcd evident that the chief 

 diflerence between common air and pefiilential air confifted 

 merely in this ; that iu the former, the fepton with caloric 

 formed azotic air, and the oxygene conftitutcd vital air, each 

 j; q diftina 



