320 iFIGURE OF THE EARTH. 



taken as tlic ten millionth part of one qnarter of the meridian just measured.* 

 In 1803 Mechain passed anew into Spain with the intention of prolonging the 

 arc of the m;.'ridian to the Balearic islands ; but being placed in detention in 

 the fortress of Mantjuich, in consequence of the ill understanding then subsist- 

 ing between his own government and ours, he took the occasion to rectify his 

 former calculations and observations, and from the mortification which he ex- 

 perienced at observing certain discrepancies, fell into a state of dej(!ction, and 

 after having been previously set at liberty, died at Castellon de la Plana in the 

 year 180-5. During the two following years, Biot and Arago, assisted by the 

 Spaniards Chaix and Rodriguez, not less worthy of participating in this work 

 than Don Jorge Juan and Ulloa in that of Peru, carried the operation to the 

 issue contcm])lated by the too scrupulous Mechain. 



The British triangulation Avas initiatcid in 1784 under the direction'^of General 

 Roy, with the twofold object of perfecting the geographical chart of the United 

 Kingdom, and at the same time prolonging towards the north the measurement 

 of a terrestrial meridian. After being suspended in 1788, these labors were 

 resumed in 1793 under the supervision of W. Mudge, who extended the geodesic 

 system to the extreme confines of Scotland, and deduced, as the value of the 

 earth's compression, the fraction 3^^, being identical with that obtained in 

 France; yet the Spaniard Rodriguez soon after demonstrated that in the course 

 of the British operations frequent and, to a certain extent, inexplicable anoma- 

 lies were distinguishable. 



After the preceding measurements the following are the principal ones in the 

 order of their dates : 



That of the arc of Lapland in 1801, undertaken with a view of verifying 

 and extending the work of Maupertius. 



That efi'v'ctcd in India, in 1802, 1803, by Colonel Lambton, from which there 

 resulted at first a flattening of ^^g^, which Rodriguez, in repeating the calcula- 

 tions, reduced to ^J q. The same Lambton inaugurated another vast operation 

 which, continued by Captain Everest, embraced an actual arc of more than 21^^, 

 from Cape Comorin to Kaliana, north of Delhi. 



That of Piedmont, 1821 to 1823, conducted by the Italian astronomers 

 Carlini and Plana. 



That of the meridian of Dorpat, begun in 1817 and 1821 by Tenner and W. 

 Struvc, and Avhich up to this time prolonged north and south fi'om the frozen 

 coast of Norway to the mouths of the Danube, comprises an' arc of more 

 Uian 25'". 



Those of Hanover and Denmark, accomplished by Causs and Schumacher, 

 it the same date with the Piedmontese triangulation. 



The Prussian, corresponding to the meridian of Kciningsberg, which, under 

 the superintendence of Bessel and Bayer, exhibits a model in labors of this 

 nature, and which it Avill be difficult for any future ones to excel. 



Besides these important triangulations, still another deserves notice, which 

 was eflccted by Maclear in the extreme south of Africa, with the object of 



' The calculations required to fix the length of tlie metre were executed by SAvinden on the 

 part of Holland, Trallcs of Switzerland. Laplace and Legendre of Franco, and Ciscar of 

 Spain. Delambio showed, not long afterwards, that, as well in the selection and analysis 

 of the elements of the calculation as in the calculation itself, not all the circumspection desir- 

 able had been observed ; a judgment which analogous worlis, effected in the coui>o of the 

 present century,' liavc fully coniirmed. The difTerence between the legal and the tiicoietic 

 metre — a difference wliicli will ncvi-r be perfectly known — is, however, very small, and abates 

 but little or not at all the mciit of the decimal metric system, which possesses, in other 

 respects, the most unrjuestionable advantages over otlier systems now in use. Still it ia 

 well to know that between (he metre and the quarter of tho meridian there does not exist the 

 simple relation which was at first supposed, that unit having been reduced to a conventional 

 tyj)e, as is also the case witli all others of its kind. 



On this subject may bo consulted the Tratado do Metcorologia Antiqua y Modcrna, por M. 

 Saigey. 



