654 PHILOSOPHICAL TRANSACTIONS. [aNNO i74Q. 



in the middle, so as to make an obtuse angle ; and the ends of these wires ap- 

 plied together, forming an acute one, the whole appeared in the shape of a lo- 

 zenge ; in the centre of which was placed the brass cap on which the card turned. 

 And so far was it from being made with any tolerable degree of exactness, that 

 there was not the least care taken either to bend the wires in the middle, or to 

 fix the cap exactly in the centre of the lozenge. The pin, on which it turned, 

 was made of a slip of plate brass sharpened to a point. 



Besides the particulars already communicated to the Society, the captain in- 

 formed him, that he was obliged to sail above 300 leagues, after this accident 

 happened, without a compass, till he arrived at Cowes in the Isle of Wight ; 

 where being provided with one, he placed it in the binacle, but was much sur- 

 prised to find that it varied from the direction it stood at when out of the binacle 

 nearly 2 points. He removed the binacle to different parts of the deck, but 

 found that it always made the needle to vary after the same manner when placed 

 in it. He repeated the same experiment lately in the river, with the like success; 

 only that he observed, that the variation of the needle, when placed in the bi- 

 nacle, was rather less than at first. It was natural to inquire if there was any 

 iron about the binacle ; but the Captain said he had given strict charge to the 

 maker not to put so much as a^single nail in it; and that he firmly believed that 

 there was not the least bit of iron about it. 



Being willing to be satisfied of the truth of a circumstance so very extraor- 

 dinary, the Captain was desired to send the binacle to a house in the city; where, 

 in company with the Captain, Mr. Ellicot, and another gentleman, Mr. K. tried 

 it with a large compass touched by his bars; but finding no sensible variation, 

 they at that time desisted, thinking the fact quite improbable; but having dis- 

 covered the effect which the lightning had produced on the wires which fastened 

 the sides of the compass box, he was induced to examine the binacle a second 

 time; which he did with a small compass, and with great care, in every part; and 

 at last, about the middle of the binacle, he found it to vary very sensibly, but 

 could not discover any nails or iron any where thereabouts; till, turning it up to 

 examine the bottom, he there found 3 or 4 large nails, or rather spikes, driven 

 through it to fasten the upright partitions in the middle of the binacle. 



It would not be difficult to explain why any needles, under such circumstances, 

 should be rendered useless by lightning, though the needles themselves had re- 

 mained unhurt. So many iron wires made strongly magnetical would doubtless 

 have effected it; and 3 or 4 large nails in the binacle, if made magnetical, 

 would alone have been sufficient to have done it. But it has already been no 

 ticed that the polarity of the needle was inverted by this accident; and he ftir- 

 ther observes, that all needles constructed after this manner are liable to be 

 rendered useless, not only by the lightning's destroying their virtue, but also by 



