VOL. LXXI.] PHILOSOPHICAL TRANSACTIONS. 115 



XVII. Account of an Earthquake at Hafodunos near Detibigh. By John Lloyd, 



Esq., F.R.S. p. 331. 

 August 29, 1781, at 8 h 37 m 30', as Mr. L. was sitting on his bed-side, he 

 heard a rumbling noise, as if at a distance : the sound seemed to approach, and 

 whenvit was greatest the bed rocked and shook so much that he could scarcely 

 keep his seat. The barometer had been stationary nearly for the 3 preceding 

 days, and did not seem to be affected with the shock. The morning was re- 

 markably fine, and not a single cloud to be seen. Two of his sisters and a gen- 

 tleman were walking on the terrace in the garden by the side of a wall : they all 

 perceived the noise, at first as if at a great distance ; but when it was greatest 

 they perceived the wall to shake, though they did not observe any agitation 

 under their feet. It continued from 15 to 18 minutes; and its course was 

 nearly from south-east to north-west. Some other persons in the house per- 

 ceived a double shock ; and this was observed by many who felt it in other 

 places. It was felt at most other parts in Wales. And 2 other shocks were 

 afterwards felt the same year in Wales. 



XVIII. On the Heat of the Water in the Gulf-Stream. By Chas. Blagden, 



M. D., F. R. S. p. 334. 



One of the most remarkable facts observed in navigating the ocean, is that 

 constant and rapid current which sets along the coast of North America to the 

 northward and eastward, and is commonly known to seamen by the name of the 

 gulf-stream. It seems justly attributed to the effect of the trade-winds, which, 

 blowing from the eastern quarter into the great Gulf of Mexico, cause there an 

 accumulation above the common level of the sea; in consequence of which, it is 

 constantly running out by the channel where it finds least resistance, that is, 

 through the Gulf of Florida, with such force as to continue a distinct stream to 

 a very great distance. Since all ships going from Europe to any of the southern 

 provinces of North America must cross this current, and are materially affected 

 by it in their course, every circumstance of its motion becomes an object highly 

 interesting to the seaman, as well as of great curiosity to the philosopher. 



During a voyage to America in the spring of the year 1776, Dr. B. used 

 frequently to examine the heat of sea-water newly drawn, in order to compare it 

 with that of the air. The passage was made far to the southward. In this 

 situation, the greatest heat of the water which he observed was such as raised 

 the quicksilver in Fahrenheit's thermometer to 774. This happened twice ; the 

 first time on the 10th of April, in latitude 21° 10' n. and longitude by reckon- 

 ing 52° w. ; and the 2d time, 3 days afterwards, in latitude 22° ^' and longitude 

 55°; but in general the heat of the sea near the tropic of Cancer about the 

 middle of April was from 76" to 77°. 



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