Dr. Per aval on the EffeSfs of Famine, ^c. 513 



of other caufesj which reftore falubrity to the air, 

 refpiration could hot be carried on, under fuch 

 circumftances. And we may obferve that frofly 

 weather, which is generally ferene and without 

 wind, always proves extremely opprcfTive, and 

 fometiines even Fatal to afthmatic patients, in 

 great cities. Indeed the rate of human mortality 

 bears a pretty near proportion to their magni- 

 tude and population: And I have fhewn, in 

 another work,§ that there is an aftonifhing dif- 

 ference between the expedation of life in Man- 

 chefler, and the country immediately furround- 

 ing it, although the inhabitants of both are fub* 

 jedl to the fame vicilfitudes of weather, carry on 

 the fame manufactures, are fupplied with pro- 

 vifions from the fame market, and by their free 

 intercourfe, are almoft equally liable to attacks 

 of fmall-pox, fevers, and other epidemics. 



It is evident, therefore, that habit, however it 

 may abate, cannot entirely countered the bane- 

 ful operation of bad air. And thofe will feel 

 its pernicious cffeds moft ftrongly, in every 

 fituation, whofe nervous fyftems are endued with 

 more than ordinary fenfibility. Such perfons I 

 would caution not to indulge their curiofity in 

 the infpedion of unwholefome manufadures 

 nor in vifiting mines, caverns, ftoves, hof[)itals, 

 or prifons. Several Gentlemen, in this afTembly, 



§ Eflays Philofophical, Medical and Experimental. 



Vol. II. L 1 will 



