244 Comparison of the french metre 



which is extended about two inches thick over a large furfaccj, 

 and left in that fituation for three months. Carbonate of foda 

 is then formed, which is warned out and cryilallized in the 

 ufual manner. The foda obtained by this procefs always has 

 a yellowifli caft. 



VII. 



Comparifon of the French definitive Metre with an Englijh Stand- 

 ard, brought from London b\j M. A. Pictet, one of the 

 Editors of the Bibliothcque- Britannique *. 



Short hiftory of J[ HE meafurement of the earth, and the inveftigation of 

 of the earth. * ts figure, were the fubjects, at various times in the courfe of 

 the eighteenth century, of the labours of a number of philoso- 

 phers of the firfl eminence in different countries. Some Swe- 

 difii aftronomers are now employed in a fecond meafurement 

 of the fame degree which was meafured fixty years ago by the 

 French Academicians in Lapland, under the polar circle. In 

 France, when the idea of feeking in the dimensions of the 

 globe itfelf the unit to which all meafures and weights might 

 be referred, had once been conceived and adopted, it was ne- 

 ceflary to make an effort proportional to the importance of an 

 particularly that undertaking which was thus become national. In the midft 

 btely made in Q f a j on g anc | f an g U ; narv war , together with difficulties of 

 every other kind, a chain of triangles has been formed between 

 Dunkirk and Barcelona, comprehending the tenth part of the 

 arc of the meridian which extends from $e Equator to the 

 pole, and which is equal to one fourth of the circumference 

 of the globe ; and the ten millionth part of this arc, thus de- 

 termined, has been adopted for the unit of the metrical fyf- 

 tern : it has been fixed by the conftruclion of flandards made of 

 fubftances proper to refill the attacks of time ; and by a careful 

 examination of the precife relation of the length of the metre 

 and the ftandard to that of the pendulum vibrating feconds, on the level of the 

 fea, in a given latitude, the determination of this unit has been 

 rendered independent of any accident that might deftroy or 



meafure thence 

 deduced 



* From No. 148 of the Bibiiotheque Britanique. I avail my- 



felf of the free tranflation given in the Journal of the Royal Inftitu- 



tion j but have very carefully read the proof with the original.-— N. 



4 impair 



