68 Anafyses of Books, [Jui^Y^ 



similar circumstances, would not have been one ten-thousandth 

 of an inch. 



" The cause was now evident, by elevating the middle of the 

 standard, the under surface was shortened, and the upper sur- 

 face extended ; and on the contrary, when the extremities were 

 elevated, the upper surface was compressed, and the lower 

 surface lengthened, the quantity of the eflPect evidently depend- 

 ing upon the thickness of the bar. 



" Having thus assured myself of the source of the error, a 

 method of obviating it soon presented itself. As the upper and 

 under surfaces of the bar are in different states, the one being 

 compressed and the other extended, there must be an interme- 

 diate plane which suffers neither extension nor compression, and 

 this plane must be nearly midway between the two surfaces. I 

 therefore caused Mr. Dollond to reduce the thickness of the bar 

 for the distance of an inch and three quarters from its extremi- 

 ties to one-half; the gold disks and plugs were then inserted as 

 before, and the adjustment completed in the manner which has 

 been described. The plugs being secured, and the projecting 

 parts removed, the standards were repeatedly compared with 

 feir G. Shuckburgh's scale (the standard being placed upon the 

 scale) when no perceptible difference could be detected. Pieces 

 of card were now placed under the standard as before, without 

 occasioning any appreciable alteration ; and I had thus experi- 

 mental proof of the perfect efficiency of the remedy I had 

 employed. 



" I have been thus particular in detailing the difficulties I 

 experienced, because they exhibit a source of very considerable 

 error which may arise from the thickness of a standard-scale, 

 and which, I beheve, has never before been suspected. 



" It may be here not unnecessary to remark, that on every 

 occasion on which I have used Sir G.Shuckburgh's scale, it has 

 fortunately been placed not only upon the same table, but upon 

 the same part of it." 



The various standards described in this paper, with the excep- 

 tion of the yards with steel terminations, are not intended for 

 common use, but to be carefully preserved for reference upon 

 extraordinary occasions. In addition to them, other weights 

 and measures of capacity were made with great care by Mr. Bate. 

 The following is a hst of the whole ; the numbers of the stand- 

 ards corresponding with those inscribed on them by Capt. Kater, 

 during the adjustment, as detailed in the memoir. 



" Standards deposited at the Exchequer, Westminster, 

 1 Imperial standard-yard with gold points. 

 1 Standard-yard with steel terminations, No. 1 . 

 1 Imperial troy pound, No. 5. 



