334 Astronomy. [Lecture 21 . 



tween Brie, Villejuif, and Monthleri, he found 

 the distance, in like manner, between Brie and 

 Monthleri to be thirteen thousand one hun- 

 dred and twenty-one fathoms. He then formed 

 a third triangle between Monthleri, Brie, and 

 Monjay; a fourth between Monthleri, Brie, and 

 Malvoisine ; and a fifth between Monthleri, 

 Monjay, and Maree ; and from all these mea- 

 sures, the distance between Mareil and Mal- 

 voisine was found to be thirty-one thousand eight 

 hundred and ninety-seven fathoms French. 



In a similar manner, by means of thirteen 

 triangles, he proceeded as far as Sourdon, near 

 . Amiens, and found the distance between Sour- 

 don and Malvoisine to be sixty-eight thousand 

 four hundred and thirty fathoms. But as cal- 

 culations are less subject to errors than me- 

 chanical operations, Mons. Picard, in order to 

 avoid every inaccuracy of this kind, took a new 

 base near Sourdon, and found its length, both 

 from a continuation of his trigonometrical ope- 

 rations, and from an actual mensuration ; and 

 as these exactly agreed, he could no longer doubt 

 of the truth of his former calculations. For the 

 two bases were separated by so large a distance, 

 that it was impossible for them to correspond, 

 except by a perfect exactitude in all the interme- 

 diate steps. 



This part of his project being finished, he had 

 now to reduce the distance between Sourdon and 

 Malvoisine to an arc of the meridian. 



