ON THE UNIFORMITY OF WEIGHTS AND MEASTJKES. 103 



be requested to give the degrees of heat or cold according to both the 

 Centigrade and Fahrenheit's thermometers. 



10. It is recommended that the scales of thermometers constructed for sci- 

 entific purposes be divided both according to the Centigrade and Fahrenheit 

 scales ; and that barometric scales be divided into fractions of the metre, as 

 well as into those of the foot and inch. 



11. That a committee on uniformity of weights and measures be re- 

 appointed, with a grant of £20. 



Prince Talleyrand, in 1790, distributed among the members of the Consti- 

 tuent Assembly of France a proposal, founded upon the excessive diversity 

 and confusion of the weights aud measures then prevailing all over that 

 country, for the reformation of the system, or rather for the foundation of a 

 new system upon the principle of a single and universal standard*. 



A Committee of the Academy of Sciences, consisting of five of the most 

 eminent mathematicians of Europe — Borda, Lagrange, Laplace, Monge, and 

 Condorcet — were subse(]uently appointed, under a decree of the Constituent 

 Assembly, to report upon the selection of a natural standard ; and the Com- 

 mittee proposed in their Report that the ten-millionth part of the quarter of 

 the meridian of Dunkirk should be taken as the standard unit of linear 

 measure. 



Delambro and Mechain were appointed to measure an are of the meridian 

 between Dunkirk and Barcelona. They commenced their labours at the most 

 agitated period of the French revolution. At every station of their progress 

 in the field-survey they were arrested by the suspicions and alarms of the 

 people, who took them for spies or engineers of the invading enemies of 

 France. The result was a very wonderful approximation to the true length, 

 and one in the highest degree " creditable to the French astronomers and 

 geometricians, who carried on their operations, under every difficulty and at 

 the hazard of their lives, in the midst of the greatest political convulsion of 

 modern times" t. 



By means of the arc of the meridian measured between Dunkirk and Bar- 

 celona, and of the arc measiu-ed in Peru, in 1736, by Bougner and La Con- 

 damine, the length of the quarter of the meridian, or the distance from the pole 

 to the equator, was calculated. This length was partitioned into ten millions 

 of equal parts, and one of these parts was taken for the unit of length, and 

 called a metre X, from the Greek word nerpov {a measure). 



If the arc of the meridian be calculated from the result of French researches, 

 the metre itself is equal, in English measirrement, to 39-37079 inches ; and 

 m\xltiplying this length by 10,000,000, the length of the quadrant of the 

 meridlian, when converted into feet, will be, 32,808,992 feet. Sir John 

 Herschel estimates the length of the quadrant of the meridian at 32,813,000 

 feet ; so that, according to his calculation, there is a diiference between the 

 French and the new estimate of the quadrant, of 4008 feet, and therefore the 

 French length of the quadrant is g-pVr^^ too short, aud the metre is ^J-^th 

 of an inch less than the length of the ten-miUiouth part of the quadrant. 



An error of ^J^-th of an inch in the determination of the metre is 

 more than counterbalanced by the extreme simplicity, symmetry, and con- 

 venience of the metric system. Professor Bessol observed with respect to 



* Eeport of John Quincy Adams on Weights and Measures, p. 49. Washington, 1821. 

 . t Essay on the Yard, the Penchilum, and the Metre, by Sir John F. W. Herschel, 

 Bart., K.H., M.A., F.E.S., &c., p. 19. London, 1863. 



X Briot's 'Arithmetic,'translatedby J. Spear, Esq.,p.l52. E. Hardwicke : London, 1863. 



