Additional Notes. 479 



df 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 iri 

 JEtiglandy that I transmitted not an account of it sooner. But 

 I had other affairs of more importance to me ; and it was 

 owing to an accident which gave me some uneasiness, viz. 

 his attempting to puhlish some account of it in print here, 

 that I transmitted it at last, in May, 1732, to Dr. H alley, 

 to whom I made no doubt but the invention would appear 

 entirely new ; and 1 must own I could not but wonder that 

 our good will at least was never acknowledged. 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 instruments. I only 

 wish that the ingenious inventor himself might, by some 

 means, be taken notice of, in a manner that might be of 

 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 lOOdeg. well gradu- 

 ated and numbered both ways; the radius 20 or 24 inches; 

 the curve at the centre to be one-twentieth of the radius on 

 each side, that is, one-tenth of it in the whole; the radius of 

 that curve -j-Vo P^rts of the radius of the instrument; that the 

 glass for the solar vane should not be less, but rather larger 

 than a silver shilling, with its vertex very exactly set; and 

 tliat the utmost care be taken to place the middle of the curve 

 exactly perpendicular to the line or radius of 45 deg. as tlie 

 observer must also take care that the two vanes on the limb 

 be kept nearly equidistant from that degree. To which I shall 

 only add, that it may be best to give the horizontal vane only 

 one aperture, not two. The rest, 1 suppose, may be left 

 to the workman. Thus, doubting I have already been too 

 prolix on the subject, to which nothing but a sincere inclina- 

 tion to promote any thing that might contribute to a public 

 benefit, and to do some justice to merit, could induce me, I 

 shall only request that what I have here offered may be con- 

 strued by that intention. 



J. LOGAN. 



Philadelphia, June 2S, 1734. 



* All these circumetances of Mr. Logan's complaint, and almost every 

 thing that follows to the end, except the directions for making the in&tru- 

 nient, are left out of the account published in the Plj'Uowphical Transac- 

 tions, wiiich strengthens the conjecture that justice has not been done to 

 the original invjiiitor. 



