5Q2 PHILOSOPHICAL TRANSACTIONS. [aNNO 1733. 



Example 2. — If n be put infinite, the cliaiiieter of st will be to the diameter 

 of HI, as /- to ], or 1 to v' 14; that is, as ] to 3^ nearly. 



The bottom of the vessel v, and the ends of the tubes, ought to be made 

 rather round than fiat, for their more easy motion up and down in the fluid. 

 It will be convenient to have a small basin fixed on the star, to contain shot, 

 for the more easy poising the barometer in the fluid. 



y/w ylccount of a Booh, intitled, Chrisliaiti Ludov- Gersten Tentamina Systematii 

 novi ad miitaliones Barometri ex natura elateris a'erei demonstrandas, cut 

 adjecta sidijinem, Disserlalio Roris decidui enorem antiquum et vulgarem per 

 observationes et experimenla nova excutiens. Francofurti 1733, in 8vo. 

 N° 427, p. 43. 



This essay consists of 3 chapters; the first is wholly mathematical, contain- 

 ing a new theory concerning the propagation of tremulous vibrations along a 

 series of contiguous elastic bodies. The second applies this theory to the solu- 

 tion of the chief appearances of the baroscope; and the last explains the several 

 states or constitutions of the air and weather connected with them. 



The particles of air, says Mr. Gersten, however unknown in other respects, 

 are very well known to be capable of receiving and propagating tremulous vibra- 

 tions; from hence it follows, as also from some principles of Sir Isaac Newton, 

 that the air may be dilated by repeated tremulous vibrations; and these vibra- 

 tions may be generated or produced by a confused motion of the particles of 

 the air, or by the agitation of a wind. 



The author, in prop. 7 and 8, undertakes to demonstrate, that the dilatation 

 produced by the motion of a wind, is less when the ambient air has a motion 

 the same way, than if the wind moved with the same sensible velocity against 

 the quiescent atmosphere; but that this dilatation would be greater, if the 

 atmosphere had a flux or current in a direction contrary to that of the wind. 



He demonstrates, that a perpetual easterly wind will reign in all places within 

 the tropics, arising from the diurnal heat; and that this wind will diffuse itself 

 to the other regions without the tropics, and have a direction declining from 

 the east towards the north or south, according to the situation of the region 

 on the terrestrial globe; that its motion will be more remiss, the nearer the 

 places are to either pole, and that the angle of declination from the east will be 

 greater for the same reason. 



The preliminary propositions being settled, he proceeds to account for the 

 rising and falling of the mercury in the barometer thus. The air of the atmos- 

 phere in our regions has a natural motion or current, whose direction is situated 



