r46f Of the insalubrity or FLAT 



in a country where population and wealth do not bear 

 a due proportion to the extent of territory. 



We ought however to attempt every thing in our power 

 to effe£l fo defirable and ufetul an event. 



'"hemiftry furniihes various articles by means of which 

 we can generate and introduce a fupply ot oxygen into 

 the atmofphere, as well as alter the quality of thofe 

 noxious gafes with which it is occafionally contami- 

 nated. 



Thefe however can only be employed in a very limit- 

 ted and partial manner, and of courte can only produce 

 a limited and partial amendment. 



I fhall therefore mention only a few of the fubftances 

 that may be occafionally employed for this purpofe. 



A large portion of oxygen may be furnilhed by the de- 

 compofition of nitre, as is demonftrated from its main- 

 taining the combuftion of inflammable bodies. 



If lighted charcoal, be placed in a proper expofurc 

 to the open air it will continue to burn till the whole be 

 reduced to afhes. 



If nitre be mixed with charcoal, and when kindled 

 placed in a clofe velfel, the combuftion will continue 

 as well as if expofed to the open air ; whereas, without 

 the affiftance of the nitre, the charcoal would be imme- 

 diately extinguifhed in that fituation for want of a fup- 

 ply of oxygen. 



Mr. Scheie by heating nitre to red heat in a retort, re- 

 ceived into a moiftened bladder more than fifty ounces 

 in meafure of oxygen gas from one ounce of nitre. A 

 pound will therefore furnifti 800 ounces. 



Nitre ground with two thirds of its weight of mintum 

 and moiftened with water fo as to form a pafte, burns 

 very rapidly and emits a confidcrable quantity of pure air. 



But the grmd engine, by which, the fources that de- 

 prive the atmofpere of its falutary and vivifying priiici- 

 4 pie, 



