210 MEASURING APPARATUS OF THE 



This is a matter of opinion in which every person must judge for him- 

 self; but if we refer to the bases measured by Maire and Boscovich in 

 Italy, by Delambre and Mechain in France, by Bouguer and De la 

 CoNDAMiNE in Peru,* by Roy andMuDGE in England, by my predecessor 

 and myself in India, we shall find no very insecure test of comparison to 

 direct our judgment in forming an estimate of the superior accuracy likely 

 to be attained by the new apparatus. I select these instances because I 

 am not aware of any other operations in which two bases, verificatory of 

 each other, have been measured. To take these then in order of their dates. 



The first base was measured in the plain of Yarouqui from Carabouron 

 to Oyambaro. It was performed with wooden rods called perches, pre- 

 pared on the spot from a comparison with the iron toise. It was com- 

 menced on the 3d October, and ended on the 3d November, 1736. The 

 ground was gone over by two parties independent of each other, and the 

 mean of the two results was 6272.6559 toises — 7.60 miles in a horizontal 

 direction. The base of Tarqui, which is in 3° 4' South of the Equator, 

 was measured in the same manner in the month of August, 1739 : it was 

 carried on through swampy ground, and the wooden rods floated on the 

 stagnant water, ("nous fumes dispenses dans ce trajet de faire usage du 

 niveau, les perches avec les quelles nous operions flottaient sur I'eau.") 



This base, reduced to the level of Carabouron, was 5258,949 toises, equal 

 to 6-37 miles, and the same distance computed from the series of triangles 

 was found to be 5260.03 toises, t shewing a variation of 1081 toise 



* The Conquestadore of 64 guns, and the Incendio of 50 guns, sailed from Cadiz Bay, May 

 26th, 1735. Bouguer, Godin, and De la Condamine, sailed from la Rochelle, in a Royal vessel 

 16lh May 1735. 



24th November embarked at Portabello, in company with the Spanish gentlemen; on the 

 10th June 1736, all the party assembled at Quito. 



Dans un des intervalles de ce travail nous observames, le 19th Septembre au soir, I'Eclipse de 

 la Lune. Tandis qu'on prepar it lesaperches que devaient nous servir a mesurer la base. 



f 5260 toises = 6 miles 3 furlongs. 



