172 Analysis of Scientific Books and Memoirs. 



For the lofty summit of Chimborazo, four time-keepers gave alterations of 

 rate, represented respectively by + 6. "1, + 7."0, — 5."3, and 9."1 ; and for 

 the elevation attained by Gay Lussac in his magnificent aerostatic ascent, 

 when the barometer sunk to 12.95 inches, Mr Harvey found alterations of 

 rate denoted respectively by + 13."2, and + 19."2. 



In the second branch of the experiments, relating to the influence of 

 condensed air, Mr Harvey found the results to be precisely the reverse of 

 those produced in rarefied air ; — that is, if a Chronometer gained by being 

 placed in air of a less density than that afforded by the ordinary state of 

 the atmosphere, it lost, by being subject to air of a greater. This was 

 verified by many experiments, with the same Chronometers as employed 

 under the receiver of the air pump. We select, by way of illustration, the 

 time- keeper, of which the results produced under the receiver of the air 

 pump, are contained in the fourth column of the first table of this abstract. 



And which, it will be perceived, are all decr-ements, whereas in the experi- 

 ments performed in the rarified air with the same Chronometer, they were 

 uniformly found to be increments. The almost perfect restoration of the 

 detached rate, after the great changes produced by so considerable an aug- 

 mentation of density as that corresponding to the mercurial column of 75 

 inches, is a very remarkable circumstance. 



The third division of the paper also contains some valuable and import- 

 ant results, one of which we select. An opportunity was taken, observes 

 Mr Harvey, when two Chronometers had been under the diminished pres- 

 sure of 23 inches for five days, to remove them for a like period into the 

 condensing engine, containing air of a double density. The result of this 

 application was, that the rate of one of the time-keepers received a decre- 

 ment of 9-"5, and the other a diminution of 10."4. Knowing, continues 

 Mr Harvey, the merits of these Chronometers, I ventured to predict, that 

 if the two Chronometers were removed from the condensed air into an at- 

 mosphere corresponding in density to 21 inches of quicksilver, the transi- 

 tion would produce rates greater than those corresponding to 23 inches. 

 The result verified the conjecture ; the average rate of the first time- 

 keeper being found to be + 5-"0, and of the second +12."0. 



We must, however, hasten to the fourth and last division of Mr Har- 

 vey's paper ; — relating to the question, How far the ordinary changes in 

 the density of the air are likely to exercise an influence on the rate of a 

 time-keeper ? This branch of the investigation is enriched by many deli- 

 cate experiments, relating to small changes in the atmospheric density, and 



