276 PROCEEDINGS OF THE AMERICAN ACADEMY 



Inches. 



Brass bar 2 = 36.000280 by Shuckburgh [10-46 in ]. 



= 36.000084 by Shuckburgh [0-36 in -, Kater]. 

 = 36.000229 by Eater's scale. 

 = 36.000303 by A x compared in 1834. 

 = 36.000275 by A, compared in 1834. 

 Mean, 36.000234 

 He assumed : — 

 Brass bar 2 = 36.00025 inches of the lost imperial standard at 62° 

 Fahrenheit. 



It is stated both in Appletons' and in Johnson's Encyclopedias that 

 the yard of the Astronomical Society is the principal authority upon 

 which the new standard rests. It will be seen from the above that this 

 statement is erroneous. 



The Imperial Standard Yard, known as " Bronze 19," or, according 

 to the new nomenclature, as No. 1, was constructed according to this 

 equation. It is made of Baily's metal, and has the following dimen- 

 sions, viz. : — 



Length = 38 inches. 



Width = 1 inch. 

 Depth = 1 inch. 



Gold plugs are inserted in wells sunk one half of the depth of the 

 bar. The graduations are on these gold plugs. 



Through the kindness of Mr. Chaney, the Warden of the Standards, 

 I have recently had the pleasure of assisting him in comparing my own 

 working standard yard with this bar. I have never seen lines better 

 adapted to exact measurements. They have remarkably smooth edges, 

 and are about one three-thousandth of an inch in width. Even fin- the 

 most rigid scientific investigations, they are in every respect of unri- 

 valled excellence. 



Bronze No. 1 is the national standard, and is kept in what is known 

 as the "Strong Room" of Old Palace Yard. Besides this bar, four 

 Parliamentary copies were made, of which one copy is kept at the 

 Royal Mint, one is in charge of the Royal Society, one is immured in 

 the new Westminster Palace, and the other is kept at the Royal Ob- 

 servatory, Greenwich. Forty copies were prepared on Baily's metal. 

 Of these only two are exactly standard at 62°, viz. Bronze 19, and 

 Bronze 2<S, which is kept at the Royal Observatory as an accessible 

 representation of the national standard. All the other copies have an 

 equation with respect to No. 1 ; but instead of giving this equation, 



