Scientific Memoranda. 337 



An error of this magnitude, occurring in a narrow channel and 

 in a dark night, were it unknown or disregarded, might lead to 

 the most fatal consequences ; and the disaster might perhaps be 

 erroneously ascribed to the prevalence of a powerful current, 

 the existence of which was before unknown. 



The Thetis sailed from Rio Janeiro, in December last, with a 

 million of dollars on board, in the finest weather, directing her 

 course to the S. E. The next day, thinking they were clear of 

 land, they tacked, and were sailing at the rate of nine knots, 

 when the first intimation they had of being near land, was the 

 striking of the jib-boom against a high perpendicular cliff, which 

 broke the bowsprit short off, and sent all three masts over the 

 side ; thus, in a moment, bringing utter destruction on this fine 

 vessel and her valuable cargo. The author shows that the de- 

 viation of the compass arising from the attraction of the iron, 

 was exactly of the kind which was likely to occasion this great 

 mistake in the ship's reckoning ; for the distance run by the 

 Thetis, being about eighty miles, if the local attraction of the 

 ship had been equal to that of the Gloucester, she would have 

 passed five miles nearer to Cape Frio than her reckoning, — an 

 error quite sufiicient to account for the fatal catastrophe. — The 

 author hence infers the importance of bestowing more attention 

 than has hitherto been given to the influence of the local attrac- 

 tion of vessels, and to the application of the proper means of cor- 

 rection. Philos. Mag. 



Continuation of Conybeare and Phillips's Outlines of the Geology 

 of England and Wales. — We have the best authority for announ- 

 cing, that a second volume of this celebrated work is at length 

 determined upon. Our geological readers will remember, that 

 the first volume only includes the tertiary and secondary forma- 

 tions. The entire want of a satisfactory survey of North Wales, 

 the death of Mr. Phillips, the fall which the Rev. Mr. Conybeare 

 got, and which was all but fatal, have combined with other 

 circumstances, to interrupt the continuation of the remaining 

 formations comprehended in the transition and primary Rocks. 

 There will be no reason, however, to regret the delay which 

 has taken place, since the coadjutor who is to assist Mr. Cony- 

 beare at the termination of his labours, is the Rev. Adam Sedge- 

 wick, of Trinity College, Cambridge. This gentleman has for 



