VOL. XLIII.] PHILOSOPHICAL TRANSACTIONS. 7J 



they are not fixed to any place or thing, but have a method of trailing along on 

 the sandy bottoms of creeks and rivers : they have the power not only of opening 

 and shutting their shells at pleasure, but have also the power of creeping* along 

 as it were like a snail, by turning on the upper edge that opens, and so work 

 themselves along the soft yielding sand in little furrows about half an inch deep. 

 I have traced them for several yards, by these little channels, when the tide is down, 

 and left the sands bare. 



Of an ancient Roman Inscription at Rochester in Northumberland, and two others 

 at Risingham; dated Durham, Sept. Q, 17 44. By Mr. Christopher Hunter. 

 N°474, p. 159. 



[An imperfect inscription in a stone, unexplained.] 



Some Magnetical Experiments, shown before the Royal Society, Thursday the 

 \5th of November, I744. By Mr. Gowan Knight. N° 474, p. 161. 



Mr. Knight, of Magdalen-College, Oxford, being introduced to a meeting of 

 the Royal Society on Thursday the 15th of November, 1744, produced, before 

 the gentlemen there present, several curious artificial magnets contrived by him- 

 self; some of which consisted of plain bars of steel naked, and others of bars or 

 blocks of the same substance, armed with iron after the common manner of 

 natural loadstones: but as he was apprehensive the trials he had before made of 

 the weights these magnets were respectively capable of lifting, could hardly be re- 

 peated with sufficient exactness and advantage before so large a company, he de- 

 sired to refer himself, for those particulars, to what the president of the Society 

 had seen at his lodgings on Wednesday the 7th, and on Tuesday the 13th of the 

 same month of November. 



On which the president acquainted the company, that he had lately been several 

 times at Mr. Knight's lodgings, where he had seen many experiments made with 

 his artificial magnets ; and that, particularly on the days abovementioned, he had 

 been present, and had taken minutes of the following trials then made by that 

 gentleman; by which it appeared, that, 



A small eight-cornered bar of steel, of the length of -^V inches, and about half 

 an ounce Troy weight, lifted by one of its ends about 1 \ of the same ounces. 



That another plain bar of steel of a parallclopiped form, of the length of 5 » 

 inches, the breadth -j^, and the thickness ^V of an inch, weighing 1 oz. 84- dwt. 

 lifted by one of its ends 20 Troy ounces. 



That a steel bar, almost of the same form as the last, but only 4 inches in 

 length, capped or armed with iron at each end, cramped with silver, and weighing 

 all together 1 oz. 14 dwt., lifted by the feet of the armour full 4 lb. Troy. 



* I have seen this of our horse-muscles in ponds here in England. C. M. — Orig. 



