44 Mechanical Philosophy/. 



and Messrs. Pitot, Bossut, Belidor, De la 

 BoRDA, D'Alembert, De la Grange, and De 

 BuAT, of France. 



pneumatics. 



In Pneumatics, or that science which treats of 

 the mechanical properties of elastic fluids, modern 

 discoveries and improvements have been very nu- 

 merous and important. Ever since the famous 

 Torricellian experiment, in the seventeenth cenr 

 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 tOr 

 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 their application to the arts of life. 



The Barometer has, within the last century, re- 

 ceived many and most important improvements, 

 from R OWNING, De Luc, Roy, Shuck bourgh, 

 Caswell, Nairne, Jones, and others/ The ap- 

 plication of this instrument to the measurement of 

 altitudes was first suggested by Dr. Halley, and 

 afterwards better explained and systematized, by 

 Beveral of the gentlemen just mentioned, especin 

 ally by the celebrated M. De Luc, of Geneva. 

 The Air-Pump, during the same period, was much 

 improved by Hawksbee, Gravesande, Abbe 

 NoLLET, Smeaton, Russell, our ingenious coun- 



f See Encyclopsedia, Art. Barometer and Pneumatics. See altoj 

 Fhijpsophical Transactions, vol. Ixxyii, 



