270 Description of a new Fence 



lysis, that supposing the initial velocities and their first dif- 

 ferences, divided by the element of the time, had been the 

 same with respect to the molecules situated upon the same 

 terrestrial radius, these molecules will remain upon the same 

 radius during the oscillations of the fluid. The author treats 

 the motions of the atmosphere in the same manner, looking 

 only to the regular causes which agitate it. He first con- 

 siders it in the state of equilibrium ; and comparing the con- 

 ditions resulting from this supposition with those which the 

 equilibrium of the seas necessitates, from this he infers, 

 that, in the state of equilibrium, the stratum of air contiguous 

 to the sea is every where of equal density ; and that the 

 atmospheric strata of equal density are every where equally 

 raised above the level of the sea, with very small exceptions, 

 which, in the exact calculation of the height of mountains by- 

 barometrical observations, ought nor to be neglected. 



The author afterwards examines if it is possible that the 

 molecules of air situated originally upon' the same terrestrial 

 radius, still remain upon this radius during the motion which 

 takes place in the oscillations of the sea. He shows that this 

 supposition satisfies the conditions of the motion, and of 

 ihe continuity of the atmospheric fluid : in this case the 

 oscillations of the various strata of level are the same. These 

 variations of the atmosphere produce analogous oscillations 

 m barometrical altitudes. The author determines them, and 

 shows that they are similar to all elevations above the level 

 of the sea, and proportional to the altitudes of the mercury 

 in the barometer, in the state of equilibrium, at these eleva- 

 tions. 



[To be continued.] 



XLVII. Description of a new Fence made of tori elastic 

 Wire, which lecomes invisible at a comparatively short 

 Distance, calculated for Pleasure- Grounds. By Henry 

 Howell, Esq. 

 To Mr. Tilloch, — Sir, 

 Oiiould you deem the following description, a#d the ac- 

 companying plate of a fence for pleasure- groufflfds, upon a 



new 



