STANDARD. 



this, like the pendulum, mud vary in different latitudes, 

 and is, moreover, affefted by the refillaiice of the atmofphere. 

 The operation is, in many other rcfpefts, very difficult to 

 be performed with any degree of accuracy. 



About the year 1778, the public attention was particu- 

 larly excited and directed to the fubjcft of flandards from 

 nature, by the Society for the Encouragement of Arts, 

 Manufaftures, and Commerce, in London, who advertifed 

 a premium of ico guineas, or a gold medal, as a reward 

 to any perfon who would propofe an improved means " for 

 obtaining invariable flandards for weights and meafures, 

 communicable at all times, and to all nations." Among 

 the candidates for this reward was Mr. Hatton, who pro- 

 poled the application of a moveable point of fufpenfion to 

 one and the fame pendulum, by which he intended to ac- 

 complifh the full effeft of two pendulums ; and the differ- 

 ence of 'heir lengths was to be the required meafure. Mr. 

 Whitehurll improved upon his plan by means of two pen- 

 dulums, the vibrations of which were in a ratio of two to 

 one. By this method it was generally admitted, that 

 the difference between the rods of two pendulums, whofe 

 vibrations are known, is a datum from which may be 

 derived an invariable ftandard meafure, as well as many 

 other ufeful problems relative to gravitation, to falling 

 bodies, and to the figure of the earth. By thefe experi- 

 ments it was afcertained, that the length of a feconds' pen- 

 dulum in the latitude of London, vibrating in a circular 

 arc of 3° 8', is very nearly 39.119 inches, but performing 

 the fame motion in the arc of a cycloid, the refult would be 

 39.136. 



Experiments, which were fuppofed to be ftill more accu- 

 rate, were afterwards made by Mr. Graham ; and a plan 

 was propofed to parliament, as before noticed, for adopt- 

 ing the pendulum as the llandard of length ; but it was 

 more warmly taken up in other countries. M. Talleyrand, 

 then bifhop of Autun, and Mr. Jeflerfon, the fecretary of 

 if ate in America, turned their thoughts very earnellly to the 

 fubjeft. Mr. Jefferfon propofed, in the houfe of repre- 

 fentatives, that the length of a pendulum in lat. 38°, which 

 he reckoned the medium of the United States, fhould be 

 adopted as a llandard on which to found a new fyilem of 

 weights and meafures, and his plans were approved, but 

 never carried into effcft. 



It was firfl propofed in France, that the length of the 

 pendulum fhould be made the llandard, taken in the latitude 

 of Paris (48^ 50') ; but the latitude 45° was afterwards 

 preferred, as molt likely to be univerfally received, be- 

 ing the medium between the equator and the poles. A re- 

 port to this effeft was made to the National Adembly, in 

 which it was agreed, that the meafurement fhould be en- 

 trufted to a committee of fix members of the Academy of 

 Sciences in Paris, and to fix members of the Royal Society 

 of London. But this plan was afterwards rejedlcd by the 

 academicians Lagrange, Laplace, Lalande, Borda, Monge, 

 and Condorcet, who recommended a llandard from the 

 meafurement of an arc of the meridian. As this feeras the 

 molt fcientific operation, and important change that has 

 ever been made in any fyilem of weights and meafures, we 

 fhall give a full account of it here, extrafted from their 

 conllitutional code. 



Extraft from the conllitutional laws of the new fyflem of 

 meafures in France. 



" By a decree of the 8th of May, 1790, fanftioned the 

 22d of Augull, the conllituent afiembly deliring that all 

 France fhould enjoy for ever the advantai^e that mud refult 

 from an uniformity of weights and meafure, commilTioned 

 the Academy of Sciences to determine the length of the pen- 



dulum, and thence to deduce an invariable llandard for all 

 weights and meafures. 



" The length of the pendulum, at firfl, appeared proper 

 for the bafis of the fyilem of meafures, being eafy to deter- 

 mine, and confequently to verify, if it fhould be neceflary by 

 any accidents happening to the flandards ; but it was ob- 

 ferved, that to take, as was propofed, for the unit of mea- 

 fures, the length of the fimple pendulum vibrating feconds, 

 was to employ, in order to determine a meafure of length, 

 not only an heterogeneous element, — time, but alfo an arbi- 

 trary divifion, — the 86,40odth part of the day. A meafure 

 of length was therefore preferred that did not depend on 

 any other quantity ; and it will be feen afterwards ( Precis 

 des Experiences, &c.) that obfervations of the pendulum can 

 neverthelefs be employed as a means of verifying, and even 

 of finding that unit of meafure, although they have not 

 ferved as the bafis of its determination. An unit of meafure, 

 taken on the earth even, has the advantage of being perfeftly 

 analogous to moll of the meafures that are likewife taken 

 on the earth, as the dillances between points of its furface, 

 or the extent of portions of this fame furface : it is, in faft, 

 more natural to compare the diflance of one place to an- 

 other to the quadrant of one of the terrellrial circles, than to 

 the length of the pendulum. In fhort, it was obferved, that as 

 the 1 0,000,000th part of the quarter of the meridian, or the 

 metre, diftered only from the pendulum vibrating feconds 

 at Paris about fix miUimetres, both units would have led to 

 refults almofl exattly fimilar." 



A fccond decree of the fame day commifTions the Academy 

 to appoint the moft convenient fcale of divifion for weights 

 and meafures, and alfo for monies. 



The decree of the 26th of March, 1 791, fandfioned on the 

 30th, to fix an unit of meafure, natural and invariable, and 

 which, in its determination, contains nothing arbitrary or 

 pecuhar to the fituation of any people on earth, adopted, 

 according to the advice of the Academy of the 19th of the 

 fame month, the dimenfionsof the quadrant of the terrellrial 

 meridian as the bafis of the new fyilem of meafures. 



" The quadrant of the meridian fhould be preferred to the 

 quadrant of the equator, on account of the great difficulties 

 that the neceffary operations to determine this laft element 

 would have prefented, and their verification, if it were ever 

 wifhed to have recourfe to it. The regularity of this circle 

 is not better afcertained, than the fimilitude or regularity of 

 meridians. The fize of the celellial arc anfwering to the 

 portion of the equator that would have been meafured, is 

 lefs fufceptible of being determined with precifion : in fhort, 

 every nation belongs to one of the meridians of the earth ; 

 one part only is placed under the equator." 



The new fyflem of weights and meafures, founded on the 

 meafure of the meridian of the earth, and on the decimal 

 divifion, was adopted by the law of the lil of Augull 1793, 

 under a nomenclature and on a bafis, both of which have 

 fince experienced changes. 



" This nomenclature, modified by the law of the 30th 

 Nivofe an. 2, did not admit the decimal multiples deca, heUo, 

 kilo, and myria, but only the fub-multiples deci and cenli. In 

 order to make up for this, feveral denominations in each clafs 

 of meafures had been adopted. Thus, the miliare exprefled 

 1000 metres ; t\\c grade, 100,000; the cadil cnrrefponded 

 with the litre, the cade to thi; kilolitre, the gravel to the 

 gramme, \.he grave to the kilogramme, the bar to 1000 kilo- 

 grammes ; and the words decicudil, cenlricadil, decicade, cen- 

 ticade, decigravel, cenligravet, dceibar, and centibar, expreffcd 

 the tenth and hundredth parts of thefe different units. The 

 name are was given to the meafure at prefent called hellare: 

 thv franc fhould be of the weight of 10 gravels, that is to fay, 



double 



