66 Analyses of Books, [July, 



such minute pieces of wire as might be found requisite to 

 make up the standard-weight. This button served also to lift 

 the weight by means of a strong wooden fork." 



Four standard-yards were made by Mr. Dollond, of brass, 

 one inch square ; having firmly screwed to their extremities 

 rectangular pieces of steel of the same width as the bar, and 

 projecting above its surface. The distance between the interior 

 faces of tne steel terminations was intended to be equal to the 

 length of the imperial standard-yard ; and one of them, since 

 deposited at the Exchequer, Westminster, Capt. Kater found to 

 be perfectly correct ; whilst one of the others was only '00038 

 of an inch too short, and of the remaining two, one was '00021 

 of an inch too long, and the other the same minute quantity 

 too short. 



The following section of the paper is so important, and fur- 

 nishes an example of extreme precision in these adjustments so 

 truly philosophical and interesting, that we must give it entire. 



" Adjustment of the Standard-Yards with Gold Points, 



" The standard yards last described are intended merely for 

 the purpose of sizing those employed in commerce, and the 

 trifling differences above stated may be utterly disregarded; 

 but the Commissioners of Weights and Measures thought it 

 desirable, that accurate copies of the imperial standard-yard 

 should be made, to be carefully preserved and transmitted to 

 posterity, solely for the purpose of being referred to upon extra- 

 ordinary occasions, or upon questions important to science. 



" The difficulty of transferrmg a given distance from one scale 

 to another, is well known to all who are acquainted with the 

 subject; the operation is one of considerable delicacy; and 

 notwithstanding every precaution is seldom absolutely free 

 from error. But a national standard should be accurately that 

 which it professes to be. It is not enough to determine its error, 

 as the record of this may in process of time be lost ; it therefore 

 became necessary to devise a method by which any perceptible 

 error in those standards which are the foundation of all the 

 others, might ultimately be annihilated. 



*'The four standard-yards which I am about to describe are of 

 brass, an inch and a quarter wide, and half an inch thick. This 

 thickness is the same as that of Sir G. Shuckburgh's scale, and 

 was chosen in order that both might be affected with equal 

 readiness by any change of temperature ; for as the imperial 

 standard-yard of 1760 is one inch square, 1 thought it preferable 

 to adjust the new standards by means of Sir G. Shuckburgh's 

 scale, which, as I have before remarked, does not sensibly differ 

 from it. 



" A disk of gold being let into the surface near one extremity, 

 a hole was drilled through the bar at the distance of thirty-six 



