Ofi the Coiif!ri(B'ion of a Balance.^-Sdenttjtc News, Es'f; 233 



XI. 

 Letter from Mr. TroUCHTON refpeSiinga Balance of his ConflruB'ion. 



To Mr. Nicholson. 



Sir, Fleet-ftrect, July 9, 1799. 



Y. 



OU will not, I apprehend, think yourfelf at all obliged to the perfon who communicated 

 the information exprefled in your note, page loi, vol. III. of your Journal, when I aflure 

 you, that the beam which I made for Sir Geo. Shuckburgh Evelyn, had circular rings 

 fafterted infide the cones; without which necefl'ary precaution, it would moft certainly have 

 been good for nothing. The other difference is moft trifling ; however, I will tell you, that 

 the fcnfibility of his balance is not perceptibly diminiflied, when the beam deviates three 

 degrees from the horizontal pofition ; and that the cryftal planes were fet and levelled within 

 half that number of minutes, by other means than thofe pointed out in your note; and your 

 informant may, perhaps, be able to fhew the mighty difference between the axis being in- 

 clined to the planes, and thofe planes being inclined to the axis. It is mofl true, that 

 the conical form of this beam is borrowed from that of the Royal Society: but the former 

 being defigned to weigh twelve times as much as fhe latter, I faw ample caufe, in other 

 refpefls, to deviate from that model. 



After all, thofe who are acquainted with the fimple principles of the balance, and eafe of 

 conftruiting it, will hardly think the maker of either Inflrument in queftion, entitled to any 

 higher credit than what is due to good workmanfhip : and more efpecially fo, was it generally 

 known, that there is an inftrument in the aflay-ofHce, Tower of London, and which was 

 iifed there by Sir Ifaac Newton, when he was afTay-mafler, to which the Royal Society's 

 balance bears full as great an affinity both in form and properties, as Sir George's does to 

 the latter. 



I am, fir, relying on your candour, and thankful for the information and pleafure which I 

 receive from the conftant perufal of you/ Journal, 



Your moft humble fervant, 



EDWARD TROUGHTON. 



A, 



SCIENTIFIC NEWS, ACCOUNTS OF BOOKS, &c. 



lN important work of Mr. Kirwan is now in the prefs, and nearly ready for publi- 

 cation, under the title of " Geological ElTays ; comprehending, the origin and conftitution of 

 mountains, feas, lakes, coal-mines, beds of fait, and of metallic ores, and evincing the accuracy 

 of the details of the formation of the earth and of the deluge, delivered by Mofes, from the 

 laws of nature, and the appearances it exhibits in its prefent ftate. By Richard Kirwan» 

 Efq. F.R.S.'* 



Propo^s 



