C 2& 4 J 
known, your philofophical refearches had not then 
made you acquainted with that mod remarkably an- 
tifeptic property of nitrous air. Since you favoured 
me with a view of fome aftonifhing proofs of this, I 
have conceived hopes, that this kind of air may like- 
wife be applied medicinally to great advantage. 
W. H* 
A Correction.. 
Upon re-examining Dr. Hales’s account of his 
experiments to meafure the diminution of air by re- 
fpiration (Statical Effays,Vol. I. p. 238, 4th edition),. 
1 find an error of the prefs, of ,* T for fo that the 
diminution of air by r efpiration, though very various, 
is, I believe, always confiderably lefs than by putre- 
faction, or feveral other caufes of diminution- But 
though 1 have mentioned this diminution as equal to 
feveral others, nothing material depends upon it ; 
the quality of the air thus diminifhed being, in all: 
refpeCts, the fame, notwithfianding the cauie of in- 
creafe (which, as I have obferved, in this and other 
cafes, co-operates with the caufe of diminution) be 
greater than I had luppofed. 
I did not endeavour to meafure the quantity of the 
diminution of air by refpiration, as I did that by 
other caufes ; becaufe I imagined that it had been 
done fufficiently by others, and efpecially by Dr. 
Hales. 
XX. An 
