368 Dr. INGENHOUSZ on the Salubrity 
furpaffes the land air in parity, yet there are the fame 
inconftancies in its degree of goodnefs as in the land air. 
I will not attempt to give any reafon for this incon- 
ftancy, as I have no experiments to fupport any ; but I 
think it highly deferving the attention of philofophers 
to attempt the difcovery of this phenomenon. 
This experiment being finifhed, I clofed my inquiries 
at Ofcend, arid fet off for Bruges. 
We arrived at dark, and about feven o’clock in the 
evening I tried the common air of that place, and found 
it inferior in purity to that of Qftend in above ten expe- 
riments: one meafureof it with one of nitrous air occu- 
pied 1 05, or thereabout. I had the mortification to find 
the Hoppers of the phials in which I had kept the air of 
Oflend all loofened, fo that I could not make any compa- 
rative trial with both airs. 
November 8th, I fet out for Ghent, where I fpent the 
next day, November 9th. I tried the air of that place 
about three in the afternoon, and found it better than 
that of Bruges ; for one meafure of it with one of ni- 
trous air occupied 103, or thereabout, in fever al experi- 
ments. 
As all the following trials with common air are made 
in the fame way as the foregoing, viz. by mixing one mea- 
fure of common with one of nitrous air, I will hereafter 
only 
