416 Additional Notes, 



the Royal Society's approbation, if the thing appears worthy o^ 

 it, more universally obtain in practice. It is now four years 

 bince Thomas Godfrey hit on this improvement : for his account 

 of it, laid before the Society last winter, in which he mentioned 

 two years, was wrote- in 1/32] and in the same year, 1730^ 

 after he was satisfied in this*, he applied himself to think of the 

 other, t'/z. the reflecting instrument by speculums for a h-lp in 

 tlie case of longitude, though it is also useful in taking alti- 

 tudes 3 and one of tlrese, as has been abundantly proved by the 

 maker, and those who had it with them, was taken to sea, and 

 there used in observing the latitude the winter of that year, and 

 brought back again to Philadelphia before the end of February 

 1731, and was in my keeping some months immediately after. 



It was indeed unhappy, that, having it in my power, seeing 

 he had no acquaintance nor knowledge of persons in England, 

 1 transmitted not an account of it sooner f. But I had other 

 aifairs of more importance to me j and it was owing to an acci- 

 dent which gave me some uneasiness, viz. his attempting to pub- 

 lish some account.of it in print here, that I transmitted it at last, 

 in May 1732, to Dr. Halley, to M'hom I made no doubt but the 

 invention would appear entirely new^ ) and I must own I could 

 not but wonder tliat our good-will at least was never acknow- 

 ledged. This, on my part, was all the merit I had'to claim, nor 

 did I then, or now, assume any other in either of these instru- 

 ments. I only wished that the ingenious inventor himself might, 

 by some means, be taken notice of, in a manner that might be 0/ 

 real advantage to him. 



There needs not, I suppose, much more of a description of 

 the instrument than has been given. I shall only say that the 

 bow had best be an arch of about 100 deg. well graduated and 

 numbered both ways ; the radius 20 or 24 inches ; the cuiTe at 

 the centre to be one-tvvcntieth of the radius on each side, that is, 

 one-tenth of it in the whole ;' the radius of that curve -jV? P^rts? 



* 'I'hat U, I suppose, being " saLisficd," that he had made a real 'impro'vi' 

 vient in the quadrant. ii. H» 



f All these circumstances of Mr, Logan's complaint, and almost every 

 thing that follows to tlie enU, except the directions for making the instru- 

 ment, arc left out of the account J)ublishcd in the PhHosolih'ual Transactions^ 

 •which strengthens the conjecture tliat justice has not been done to the ori- 

 ginal inventor. 



