650 PHILOSOPHICAL TRANSACTIONS. [aNNO I79O. 



duced, and placed on the 31st of July 1787, at the station near Hampton Poor- 

 house, on the very spot where, about 35 months before, the measurement of 

 the base had been completed. By commencing an operation of this nature, at 

 so advanced a season of the year, it was sufficiently obvious, that only very faint 

 hopes could be entertained of bringing it to a conclusion before the bad weather 

 would set in. But it being of much importance to get the triangles, which ex- 

 tend across the Channel, at all events executed, it was therefore proposed to M. 

 Cassini, who had been appointed by the Academy of Sciences to superintend their 

 part of the business, that he should fix the time that might suit him best for 

 meeting on the coast. Tliis proposition being readily acceded to by him, the 

 20th of Sept. was appointed for repairing to the coasts of Dover and Calais res- 

 pectively. In the mean time the operation was continued here with all imagin- 

 able care and assiduity, through the first 10 stations of the series of triangles 

 " from Hampton Poor-house to that at Wrotham-hill inclusively. 



The instrument, and the various parts of the apparatus, were then removed 

 to Dover, at which place Messrs. De Cassini, Mechain, and Le Gendre, mem- 

 bers of the Academy of Sciences, arrived on the 23d of Sept., where, in the 

 course of 2 days that these gentlemen staid, every thing was most amicably set- 

 tled with regard to the times of reciprocal observations. A great number of 

 white lights, fitted for long distances, and several reverberatory lamps, had been 

 previously provided. Having been supplied with such a proportion of the lights 

 as seemed necessary for their side of the channel, and one of the lamps, the 

 French gentlemen departed for Calais on the 25 th. For the greater part of the 

 time, the weather was extremely bad ; yet, on the particular nights when the 

 most important observations on our side were made, namely, those at Dover and 

 Fairlight Down, the nights happened very fortunately to be favourable, so as to 

 enable us to intersect, with great accuracy, the two distant points on the French 

 coast of Blancnez and Montlambert, or Boulemberg, and thereby to establish for 

 ever, the triangular connection between the two countries. In finishing the co- 

 operation with the French commissioners, at Lydd on the 17 th of October, our 

 instrument had now passed through l6 stations out of 23. There of course 

 remained yet 7 stations where it was to be placed, and observations to be made. 

 Eagerly wishing to bring the business to a conclusion, they struggled on through 

 5 of the 7. But the weather at length became so tempestuous, that it was utterly 

 impossible to continue it, with any hopes of being able to make satisfactory obser- 

 vations. On the 2d of November therefore the instrument was sent to town, 

 leaving the stations on Goudhurst and Frant Churches unoccupied till the ensu- 

 ing season, and the winter months were employed in calculating the observations 

 that had been made. 

 By various delays in repairing the instruments, the surveyors had again the 



