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XX. Of the effects of the density of air on the rates of chrono- 
meters. By George Harvey, F. R. S. E. &c. Communi- 
cated by Davies Gilbert, Esq. V . P. R. S. 
Read May 13, 1824. 
A mong the different sources of error to which chrono- 
meters are commonly considered to be liable, the effects 
of the variable density of the medium in which the balance 
performs its vibrations has, in some degree, been overlooked. 
That changes in the density of the medium, produce however 
a sensible influence on the rate of a delicate time-keeper will, 
I hope, clearly and satisfactorily appear, from the detail of 
the experiments, now respectfully submitted to the Royal 
Society. 
The investigation of the subject has been undertaken in 
the four following points of view : 
First, by subjecting different chronometers to a less pres- 
sure than that afforded by the ordinary state of the amosphere 
at the level of the ocean. 
Secondly, by submitting them to a greater pressure than 
that afforded by the atmosphere under the same conditions. 
Thirdly, by removing chronometers from condensed into 
rarified air, and vice versa. 
And fourthly, to determine how far the rates of chrono- 
meters are affected by the ordinary aberrations of atmo- 
pheric pressure at the level of the sea. 
1. To estimate the effects produced by the first of these 
