XLVIII PHILOSOPHICAL SOCIETY OF WASHINGTON. 
and with the supposed fac-simile of it made by Troughton for Pro- 
fessor Pictet, of Geneva, and thus it happened “that on the conti- 
nent of Europe all measures were converted into English units by 
a reference to Sir George Shuckburgh’s scale. The Royal Commis- 
sion of 1819, believed Bird’s standard of 1760 to be identical with 
Shuckburgh’s scale, and they legalized it rather than the standard of 
1758, in order to avoid disturbing the value of the English yard 
which was then generally accepted for scientific purposes. 
There are yet four other scales of importance in the history 
of English standards—namely, the brass five-foot scale made for 
Sir George Shuckburgh by Troughton in 1796; two iron standard 
yards, marked 1A and 2A, made for the English Ordnance Survey 
department by Messrs. Troughton and Simms in 1826-’7, and the 
Royal Society’s standard yard constructed by Mr. George Dollond, 
under the direction of Captain Henry Kater, in 1851. 
Bearing in mind the preceding history, the genesis of the present 
English standard yard may be thus summarized: In 1742 Graham 
transferred to a bar made for the Royal Society a length which he 
intended should be that of the Tower yard, but which was really inter- 
mediate between the Exchequer standard yard of Elizabeth and its 
matrix. That length he marked with the letter E, and, although 
destitute of legal authority, it was immediately accepted as the 
scientific standard and was copied by the famous instrument makers 
of the time with all the accuracy then attainable. Thus itis in 
fact the prototype to which all the accurate scales made in Eng- 
land between 1742 and 1850 can be traced. Bird’s standard of 
1758 was compared with the Exchequer standard and with the 
Royal Society’s yard E, and was of a length between the two. 
Bird’s standard of 1760, legalized as the Imperial standard in June, 
1824, was copied from his standard of 1758. After becoming the Im- 
perial standard, Bird’s standard of 1760 was compared with Sir 
George Shuckburgh’s scale by Captain Kater in 1830 and by Mr. 
Francis Baily in 1834; with the Ordnance yards 1A and 2A in 
1834 by Lieutenant Murphy, R. E., Lieutenant Johnson, R. N., 
and Messrs. F. Baily and Donkin; and with Kater’s Royal Society 
yard by Captain Kater in 1831. On October 16th, 1834, the Im- 
perial standard (Bird’s standard of 1760) was destroyed by the 
burning of the Houses of Parliament, in which it was lodged, and 
very soon thereafter the Lords of the Treasury took measures to 
