30 On certain Newer Deposits in Sicilij. 



the officers of the Royal Engineers, I observed that all the hills 

 of any magnitude were in parallel ridges, having a direction of 

 nearly north-east* and south-west, and which also corresponds to 

 that of the numerous deep narrow bays of the north coast, two 

 of the largest and most beautiful of which form the fine secure 

 harbours of La Valletta. To what this direction has been owing, 

 it wouldj I conceive, be rather difficult to determine, for it does 

 not correspond to any great fractures in the strata, all of which 

 have very nearly retained their horizontal position ; but, at the 

 same time, it is worthy of remark, that all the hills having this 

 direction appear to have been elevated above the sea before the 

 deposit of the conglomerate mentioned above, for I have been 

 assured by some intelligent persons here, that it is never seen on 

 their summits, but only in the bottom of the valleys which se- 

 parate them. 



On the Proximate Causes of certain Winds and Storms, By 

 Professor E. Mitchell, University of North Carolina. 

 (Continued from page 296 of preceding volume.) 



On the Causes of the Trade-Winds. 



W iTH the above facts and arguments before us, we are pre- 

 pared for an investigation of the proximate causes of the trade- 

 winds. Two theories have, as is well known, been advanced 

 upon this subject. The earliest is contained in a paper of Dr 

 Halley's, read before the Royal Society in 1686. The other, 

 that of Hadley, was brought forward in 1735, and as it is that 

 which is generally adopted by the oldest philosophers of the pre- 

 sent age, it may be regarded as presenting the strongest claim 

 to our particular and continued attention. It may be stated in 

 the words of Laplace. 



" The sun, which we will suppose, for the sake of simplicity, 

 iti the plane of the equator, there rarefies by its heat the columns 

 of air, and elevates them above their natural level ; they should 

 then re-descend by their weight, and be carried towards the 

 poles in the superior part of the atmosphere ; but at the same 



