378 Mr. Harvey on the effects of the density of air 
It is remarkable, that the increments resulting from the 
unequal detached rates of the chronometers B and D, should 
In two instances, viz. those corresponding to half an inch, 
and 20 inches of quicksilver, be precisely the same ; and in 
three other cases, viz. 15 inches, 10 inches, and 5 inches 
respectively, very nearly so ; the only considerable devia- 
tion being in the rate of the time-keeper D, when under 
a pressure corresponding to 25 inches of quicksilver. This 
chronometer however recovered itself when under a pressure 
of 15 inches. 
In another set of experiments, and of which the results 
are found in the succeeding table, the density of the air 
under the receiver was uniformly diminished by decre- 
ments represented by two inches of quicksilver, and which 
was accompanied by changes in the rates of the two chro- 
nometers employed, (abstracting the occasional aberrations 
displayed by most time-keepers) increasing proportionally 
as the density of the air was decreased. From the nearly 
equal uniformity of temperature also that prevailed during 
each set of experiments, and from the positions of the chro- 
nometers with respect to the magnetic meridian having 
likewise been preserved constant, there can be no doubt but 
the different alterations of rate are due to alterations of 
pressure. 
