Compari/on of the Dejinitk'e 'Metre, &c. 229 



Employment; but, fo far is that from tlie truth, they may 

 jiiftly be confidered amons; the moil difRciiIt problems ot 

 chemillry ; and it is only from the rigid and conltantly 

 (iniilar refults of fuch experiments, that we can hope to at- 

 tain an intimate knowlod'ic of the principles with which na- 

 ture has originally operated. 



[I'o be continued.] 



XXXIX. Coviparljhn of ihe Definitive Metre luith a Statulard 

 of the En^rlijh Mea/ures, carried from London^ to Paris by 

 M. A. PiCTKT, Profeffor of Phtlofophy at Geneva*. 



l\ S the mcafiircmcnt of the earth, and rcfearchcs refpe6l- 

 ing the figu-c of it, had, at various tin)ts, and in different 

 countries, during the courfo of the 18th century, been an 

 objpft of the labours of the moft diftin^ruifhed philofophcrs f, 

 when an idea was latelv conceived in France of deducing from 

 the dimonfious of our s^lobe a ftandard of unity, to which 

 every thing iulceptible of meafurement or weight could be 

 refei-red, it was neceflary to make an eObrt proportioned to 

 the importance of an enlcrprife become a national concern. 

 In the midft, therefore, of a long and dcllrmStive war, and 

 amidft a thoufand difficulties of every kind, a feries of tri- 

 angles was cltablifhcd lictween Dunkirk and Barcelona, com- 

 prehending the tenth part of an arc of the meridian extend- 

 mg from the ctjuator to the pole, that is to fiiy, the fourth, 

 part of the whole circumference of the globe ; and the ten 

 inillionth part of this arc fo determined was adopted as re- 

 prefenting the unity of the whole metric fyflem. This plan 

 was cxi-cuted with (landards compofed of iubftances capable 

 of refifting the influence of the weather; and by then ella- 

 blidiing, as was carefully done, the exaft ratio of the length 

 of the metre to that of a common pendulum which fwings 

 feconds, on the borders of the fea, in a given latitude, the 

 determination of this unity was rendered independent of any 

 cataftrophe that might alter or deliroy its types, in the con- 

 ftruction of whicli all thofe refources prefenled l)y philofophy 

 and the arts, now brought to a very high degree of pcrleftion, 

 were employed. 



On the other hand, geodefian operations, defigncd to fur • 



From B'll'li'iorijtir li'ii.ininque, ' y prifLlVor I'i<:^iet, No i4,s 

 f Swidill) ;ill roil, jiiicr* ait hdw c-ni|il(iyt-<:l in a^Mn inciiiui iiij;- a decree 

 oF ilic niLiidiao, which \v;is inc>tl'uiid in L.ipiuiid under the [>ul<.r circle 

 l>)' the French nCiidLiiiicians abovr fixty years aio. 



P 3 ^ nifli 



