meafuring Heights with the Barometer. 693 
extraordinary irregularity took place in the tube, the cor- 
responding fpaces were proportioned both ways from 
that point, whether high or low, that anfwered to the 
mean. 
The obferved and equated manometrical fpaces being 
thus laid down on the pafte-board containing the mea- 
fures of the tube; the 2 t 2 0 of the thermometer, in exadh 
proportion to the fedtions of the bore, were conftrudted 
along-fide of them : hence the coincidences with each 
other were eafily feen; and the number of thermome- 
trical degrees anfwering to each manometrical fp'ace, 
readily transferred into a table prepared for the purpofe. 
I have already had occalion to remark that, from the 
operations of the barometer alone, an approximate rule, 
or mean equation, had been obtained for the meafure- 
ment of heights; but as, among the refults, irregularities 
were now and then met with, doubts naturally arofe, 
whether the equation, inftead of being considered as uni- 
form, might not follow an increafing or diminishing pro- 
gression? Without an infinite number of observations, 
in very different temperatures above and below the zero 
of the fcale, this point could not poffibly be determined 
by the barometer : wherefore the firft and chief thing 
propofed to be difcovered by the manometrical experi- 
ments was, whether common air, occasionally rendered 
4 U 2 more 
