VOL. XLI.] PHILOSOPHICAL TRANSACTIONS. 451 



The other fact is this : that when our ships return from the West Indies 

 through the gulph of Florida, and are got into the wide ocean, they have a re- 

 gular wind at south-west, or near that point, which sometimes attends them to 

 their very port. This wind cannot have its rise in that ocean, nor cm it come 

 from any continent that lies to the north, or even west of it ; therefore pro- 

 bably it must be an eddy of the trade-wind. 



From America to the west of England this wind glides over the ocean, a 

 plain field, that gives no opposition, and which, with its natural warmth, 

 encourages the waft, by making the air over it more ready to yield to the im- 

 pelled force. Having thus opened a passage for the trade-wind to flow even to 

 us, with a back stream; and admitting this conjecture to be right, we have the 

 cause why the south-west wind blows with us ; and then there can be no great 

 difficulty in finding out the reason why it brings so much rain. For this wind 

 blowing over a warm ocean, which sends up many vapours, by the time it 

 reaches us, it comes charged with an infinite mass of watery bladders, which 

 the cold of this climate condenses, and then they descend in showers of rain. 



Notahilia qucedam in Itinere Alpino-Tyrolensi observata per Baltkasarem 

 Ehrhartum,* M. D. Memingensem in Epistola ad C. Mortimerum, R. S. 

 Seer, missa. N° 458, p. 547- 



This paper contains some observations (not interesting in the present ad- 

 vanced state of geology) relative to the structure and formation of the Tyrolese 

 Alps, together with an enumeration of the plants found growing on that chain 

 of mountains. 



The Figure of a Machine for grinding Lenses spherically. By Mr. Samuel 



Jenkins. N° 459, P- ^55. 



Fig. 8, pi. 9, represents this machine, which is contrived to turn a sphere 

 at one and the same time on two axes, which cut each other at right angles, 

 with equal velocity and pressure on each of them. Without any skill or care in 

 the workman, it will produce a segment of a true sphere, barely by turning 

 round the wheels. 



A represents a globe covered with cement, in which are fixed the pieces of 

 glass to be ground. 



• Author of several works on natural history, the chief of which is an account of plants used in 

 the arts, in agriculture, and in medicine, written in German, and amounting to 12 vols. 8vo. Of 

 the 12 vols, seven were edited by Gmelin after the author's decease. 



3m2 



