622 
MR. AIRY’S ACCOTIN'T OF THE CONSTRUCTION OF 
Section III. — Appointment of the Treasury Commission of 1838 ; its proceedings and 
Report. Appointment of the Treasury Commission of 1843 ; its proceedings to the 
death of Mr. Baily in 1844. 
Section IV. — Proceedings of the Committee and of Mr. Sheepshanks to .June, 1847 ; 
construction of new Thermometers ; and erection of Comparing Apparatus : description 
of the Apparatus, and of Mr. Sheepshanks’ method of comparing. 
Section V. — Proceedings of Mr. Sheepshanks to the middle of 18-50 ; preparation of 
Thermometers; adoption and rejection of “Brass 2” as Basis for the new Standaixl 
Yard ; adoption and rejection of “ Split Plug A adoption of “ Bronze 12 experiments 
on thennometric expansion; comparison of Bronze 12 with several bars; first suspicion 
of personal equation ; rejection of Bronze 12 as Basis, and final adoption of “ Bronze 28.” 
Section VI. — Operations of important character to the end of 1853 ; comparison of a 
small number of bars with Bronze 28 ; investigation of Personal Equation ; investigation 
of the effect of Inside or Outside position of the bar ; investigation of the relative ther- 
mometric expansion of Steel, Wrought Iron, Cast Iron, Copper, and Brass, as compared 
with Bronze; trial and rejection of Baily’s Apparatus. 
Section VII. — Comparisons of numerous bars from 1851 to 1855 ; suspicion of change 
in Bronze 28 ; removal of the suspicion ; close of the operations on bars defining the Yard 
by line-measure. 
Section VIII. — Formation of End-measure Bars. 
Section IX. — Closing proceedings of Official Character; Extracts Rom the Final 
Report of the Commission ; Extracts from the Act of Parliament legalizing the Xew 
Standard ; standard temperatures for the compared bars ; disposal of the bars. 
Section I. — Histm'y of the British and of some Foreign Standards, ami of the methods of 
using them in Base-Measures and Pendulum-Measures, anterior to the legalization of 
the Inyperial Standards hy the Act of Parliament of 1824; defnition of the Standard 
of Length by that Act ; and provision for its restoration in case of loss. 
The principal materials for the history of the Standards are to be found in the follow- 
ing works: — 
Philosophical Transactions, 1742-1743, page 185, &c. Account of the lajing down 
of the measure of 3 feet from the Tower Scale upon the Brass Bar of the Royal Society ; 
and comparison of the Yard with the Half-Toise. [The measure thus laid down was 
marked E, apparently to denote “ English measure ” as distinguished from the French 
measure compared with it.] 
Philosophical Transactions, 1742-1743, page 541, &c. Comparisons by Graham 
(under tlie superintendence of a Committee of the Royal Society) of the Royal Society’s 
Standard, defined by two points ; the Exchequer end-standard, reputed to be the 
National Standard ; the Exchequer standard-beds ; the Tower standard-scale ; the Guild- 
hall standard-beds ; and the Clock-Makers’ standard-bed. The comparisons were made 
by the use of various kinds of beam-compasses, not described. It seems that, at the end 
