170 Analysis of Scientific Books and Memoirs. 



II. On the Effects of the Density of Air on the Rates of Chronometers. 

 By George Harvey, Esq. F. R. S. E., &c. From the Philosophical 

 Transactions for 1824, Part II. 



In the first number of this Journal, we gave a brief notice of Mr Har- 

 vey's investigation of the remarkable alterations of rate produced in Chro- 

 nometers, by changes in the density of the medium in which they are 

 placed, and we purpose now offering to our readers an analysis of the en- 

 tire memoir. 



The subject was undertaken by Mr Harvey, in the four following points 

 of view : — 



First, By subjecting different Chronometers to a less pressure than that 

 afforded by the ordinary state of the atmosphere 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 Foio'thly, To determine how far the rates of Chronometers are af- 

 fected by the ordinary aberrations of atmospheric pressure at the level of 

 the sea. 



To estimate the effects produced by the first of these conditions, the 

 Chronometers were placed beneath the capacious receiver of a large double- 

 barrelled air-pump, the pressure being indicated by an excellent mercurial 

 guage ; and for the second, the time-keepers were introduced into a con- 

 densing engine, furnished with an appropriate guage. To prevent any ir- 

 regular effects from the unequal action of terrestrial magnetism, the posi- 

 tion of each Chronometer, with respect to the meridian, was preserved 

 constant during the whole course of experiments. 



The first Chronometer, selected by Mr Harvey, was an eight-day one of 

 the box kind. Its rate for ten days previous to the experiments was 

 steady and uniform, amounting to — 3."1, the mean pressure of the at- 

 mosphere being 30.1 inches; but when placed beneath the receiver of the 

 air-pump, under a constant pressure of 20 inches of the mercurial column, 

 the mean of four days' observation gave an equally steady rate of — l."3. 

 the Chronometer having gained l."8, by diminishing the density of the 

 air in the ratio of 3 to 2. A proportional effect was produced under a 

 twenty inch pressure, and an alteration of + 9."7 was effected, by dimi- 

 nishing the density in the ratio of 30 to 1. 



The next experiment was with three pocket Chronometers, and the in- 

 crements to the rates, by diminishing the density in the ratio of 60 to 1, 

 were respectively + 18."8, + 18."3, and + 19-"9. 



In another set of experiments, the density of the air was uniformly di- 

 minished by decrements represented by two inches of quicksilver, and 

 which was accompanied by changes in the rates of two Chronometers, (ab- 

 stracting the occasional aberrations displayed by most time-keepers,) in- 

 creasing proportionally as the density of the air was diminished. From 



