183 



" Opatrum subsulcatuin, Dej. 



" Numerous elytra, and parts of the body and legs. 



" Sclerum, sp. 



" Several elytra and abdomen. Query S. lucasii near S. foveolatum, but 

 larger and more distinctly marked. 



Some of the gizzards contained remains of land or fresh-water shells. The 

 only one sufficiently perfect to ascertain was submitted to Dr Baird of the British 

 Museum, who writes to me — ' Your shell appears to be identical in shape and 

 size with the Paludina bulimoides of the Nile. This species varies much in 

 colour and markings, but not in form.' The colours in this case were de- 

 stroyed by the process the birds had undergone. — W. J. 



071 the Circulation of the Atmospheres of the Earth and the 

 Sun. By Joseph John Murphy, Esq. (Plate T.) 



Were tlie atmosphere not acted on by beat, it would be 

 everywhere at rest, and every level surface, at whatever 

 height, would be an isobarometric surface, or surface of equal 

 barometric pressure. The earth's rotation cannot produce 

 currents, but it modifies them when they are produced by 

 the action of heat. 



The greater heat of the equatorial regions expands the 

 air, and thus causes the upper surface of the atmosphere to 

 stand at a higher level there than in the polar regions. 

 This difference of level produces an outflow in the upper 

 strata of the air towards the poles ; this outflow causes a 

 partial vacuum in the lower strata, and an inflow of air to- 

 wards the equator at the earth's surface. This inflow con- 

 stitutes the trade-winds. The east component of the motion 

 of those winds is due to the fact that they come from a 

 higher latitude, where the earth's rotation is less rapid ; they 

 carry their less velocity with them, and thus have a relative 

 motion from the east, or against the earth's rotation. 



The upper currents, on the contrary, coming from a lower 

 latitude, where the earth's rotatory velocity is greater, carry 

 their greater velocity with them ; they consequently move 

 more rapidly than the earth itself in the latitudes to which 

 they are impelled, and become south-west wdnds in the 

 northern hemisphere, and north-west in the southern. 



