422 



ances great in proportion to the amount of vapour condensed. In 

 tropical regions, where the aqueous material is abundant, the dis- 

 turbances are great, but take place principally in the higher regions 

 of the air. The diminution of atmospheric pressure within the tro- 

 pics at the surface of the earth, as measured by the barometer, 

 extends over a large surface, but is not great in any one place. In 

 cooler latitudes condensation takes place nearer to the surface of the 

 globe, and then reduction of pressure is confined to a smaller area ; 

 but in parts on the surface within that area the reduction is great, 

 because the lower and therefore heavier gases have been warmed and 

 expanded ; hence the falls of the barometer in certain cool localities 

 are the greatest. In very cold and dry regions, as a consequence of 

 there being but little vapour in the air to be condensed, the barometer 

 sinks only a little, and that sinking is generally confined to a small 

 area. In accordance with this view, it was shown that, in certain 

 places, where much continuous rain falls, the barometer has a low 

 average ; and towards these areas winds blow from distant parts, as 

 in the great trade- and other winds. Sea-breezes were also shown to 

 be consequences of the condensation of vapour, which had been pro- 

 duced by the morning sun ascending to sufficient elevations ; whilst 

 the land-winds at night are attributable to the cooling of those ele- 

 vated parts by evaporation during the absence of the sun. 



Various objections that had been made to this theory of atmo- 

 spheric disturbances were noticed by the author of the paper, which, 

 though admitted to be plausible, were stated to be invalid, whilst the 

 most important meteorological phenomena were asserted to be in 

 accordance with it. 



Ill, "On the Structure and Development of the Cysticercus 

 Cellulose as found in the Muscles of the Pig." By GEORGE 

 RAINEY, Esq., M.R.C.S.E. Communicated by ft. D. 

 THOMSON, M.D., F.R.S. Received January 16, 1857. 



The observations detailed in this Communication were made known 

 to the Society on a former occasion ('Proceedings,' Dec. 13, 1855), 

 and are now reproduced with illustrative figures and suitable refer- 

 ence to contemporary researches on the origin and metamorphosis of 

 the Cystic Eutozoa. 



