VOL. LXXXIII.] PHILOSOPHICAL TRANSACTIONS. 32/ 



the winds. After a long interval of moderate westerly gales, it may be hardly 

 perceptible ; for a very few miles of northing, in the 24 hours, will be referred 

 to bad steerage, or some other kind of error : but after hard and continued gales 

 from the western quarter, the current will be felt in a considerable degree of 

 strength ; and not only in the parallel of Scilly, but in that of the south-west 

 coast of Ireland likewise. 



Our observation of what passes in the most common waters, is sufficient to 

 show how easily a current may be induced, by the action of the wind, on the 

 water contiguous to a bank, when the wind blows along it. In a canal of about 

 4 miles in length, the water was kept up 4 inches higher at one end, than at the 

 other, by the mere action of the wind, along the canal. This was an experi- 

 ment made, and reported to me, by the late Mr. Smeaton. We know also the 

 effects of a strong south-west or north-west wind, on our own coasts : namely, 

 that of raising very high tides in the British Channel, or in the Thames, and on 

 the eastern coasts : as those winds respectively blow : because the water that is 

 accumulated, cannot escape quick enough, by the Strait of Dover, to allow of 

 the level being preserved. Also, that the Baltic is kept up 2 feet at least, by a 

 strong N. w. wind of any continuance : and that the Caspian Sea is higher by 

 several feet, at either end, as a strong northerly or southerly wind prevails. 

 Therefore, as water pent up, in a situation from which it cannot escape, acquires 

 higher level, so in a place where it can escape the same operation produces a 

 current; and this current will extend to a greater or less distance, according to 

 the force with which it is set in motion ; or, in other words, according to the 

 height at which it is kept up, by the wind. I shall now adduce the facts, on 

 which the idea of the current is founded. 



In crossing the eastern part of the Atlantic, in the Hector, East India ship, 

 in 1778, we encountered, between the parallels of 42 and 4Q, very strong 

 westerly gales ; but particularly between the l6th and 24th of January, when at 

 intervals it blew with uncommon violence. It varied 2 or more points, both to 

 the north and south of west, but blew longest from the northern points ; and it 

 extended, as I afterwards learnt, from the coast of Nova Scotia, to that of 

 Spain. We arrived within 6o or 70 leagues of the meridian of Scilly on the 

 30th of January, keeping between the parallels of 49 and 50; and about this 

 time we began to feel a current, which set the ship to the north of her intended 

 parallel, by nearly half a degree, in the interval between 2 observations of lati- 

 tude ; that is, in 2 days. And the wind, ever afterwards inclining to the 

 south, would not permit us to regyin the parallel ; for though the northern set 

 was trifling, from the 31st till we arrived very near Scilly ; yet the wind, being 

 both scant and light, we could never overcome the tendency of the current. 

 Add to this, that the direction of the current, being much more westerly than 



