52 Mechanical Philosophy, [Chap. I. 



meroiis and important. Ever since the famous 

 Torricellian experiment, in the seventeenth cen- 

 tury, proved that air was a gravitating substance, 

 the attention of philosophers has been employed, 

 with great success, in investigating the properties, 

 and ascertaining the laws of this fluid. By nume- 

 rous and patient inquiries, they have gone far to- 

 ward reducing to regular system the principles 

 which govern the density, the weight, the elasti- 

 city, and the motions of the atmosphere. And 

 the various mechanical properties of air, as they 

 became, in succession, better understood, have been 

 rendered subservient to the utility of man, by tlieir 

 application to the arts of life. 



The Barometer has, within the last century, re- 

 ceived many and very important improvements, 

 from Rowning, de Luc, Roy, Shuckburgh, Cas- 

 well, Nairne, Jones, and others*. The application 

 of this instrument to the measurement of altitudes 

 was first suggested by Dr. Halley, and afterwards 

 better explained and systematised, by several of 

 the gentlemen just mentioned, especially by the 

 celebrated M. de Luc, of Geneva. The Air-Pump, 

 during the same period, was much improved by 

 liawksbee, Gravesande, abbe Nollet, Smeaton, 

 Russell, the rev. Dr. Prince, of Salem in Ame- 

 rica f, Lavoisier, and fmally Cuthbertson, of Am- 

 sterdam; by the last of whom, we are taught 

 to beheve, this machine has been carried to a 

 degree of perfection beyond which little advance- 



* See Ejwj/clopa:dia, Art. Barometer and Pneumatics. Sea 

 alio Philosophical Transactions^ vol. Ixxvii. 



t Sec the TransuQiions of the Jmcr. A^ad, of Arts and Sciences, 

 vol. i. 



