278 PROCEEDINGS OF THE AMERICAN ACADEMY 



the one from which Chisholm obtained his value of the equation between 

 the meter and the yard. It is now the working standard meter of the 

 Exchequer. 



A second natural unit, viz. one ten-millionth part of a quadrant of 

 the earth's surface, was adopted at the close of the last century as the 

 basis of the metric system. In March, 1791, a committee of the Insti- 

 tute of France, consisting of fifteen members, including Borda, La- 

 grange, Laplace, Monge, and Condorcet, recommended this unit as a 

 standard of linear measure. It is interesting to note that the Com- 

 mission was largely international in its composition. Besides the mem- 

 bers of the Institute, there were delegates from the Republic of the 

 Netherlands, from Sardinia, Denmark, Spain, Tuscany, the Roman 

 Republic, the Cisalpine Republic, the Ligurian Republic, the Swiss 

 Confederation, and from Piedmont. Their report wa% sanctioned by 

 the Assembly, and an arc of the meridian passing through Paris, and 

 extending from Dunkirk to Barcelona (stations differing about 10° in 

 latitude), was measured with great care by Mechain and Delambre. 

 By combining the results of this survey with arcs previously meas- 

 ured in Peru and Sweden, the length of a meridional quadrant passing 

 through Paris was ascertained. For the measurement of base lines, 

 two separate toise end-measures were employed, each assumed to 

 be equivalent to the toise of Peru. From these standards, four iron 

 bars were prepared, having their ends carefully ground and polished 

 until they were exactly comparable with each other, and until each 

 had the required length. One of these original bars, bearing upon it 

 the stamp of the Commission, is now in the possession of the United 

 States Coast Survey. It is understood to be the only copy now in 

 existence. One bar was chosen as the standard of France, and from 

 it was constructed the platinum " Metre des Archives." Two similar 

 meters, made at the same time and in the same manner, are now 

 in existence, viz. the "Metre du Conservatoire," and the "Metre de 

 l'Observatoire." All of these meters are end-measures, and have about 

 the same dimensions as the English platinum meters already described. 

 The equation between the "Metre des Archives" and the "Metre du 

 Conservatoire" is small. That between the " Metre des Archives " and 

 the " Metre de l'Observatoire" is not well determined. Only one line- 

 measure is known to have been made at the time of the construction 

 of the end-measures. This was transferred from the " Metre de l'Ob- 

 servatoire," probably about two years after the adoption of the "Metre 

 des Archives " as a standard. 



In 1870, a commission was formed at Paris, under the title "Com- 



