41 6 Mdjor-Genera! V^oy'^s Account of the 



lids ; one a femi-circle, with the central point marked by a. 

 line cut on its diameter, brougl:it into the dire(5lion of the bafe; 

 with which line the gilt wire, fufpended at the extremity of 

 the firft rod, was made to coincide on the commencement of 

 the meafurement. The other lid has a very fmall hole made 

 in its center, through which the plummet wire is to pafs, 

 when fufpended from the center of theinftrument, hereafter ta^ 

 be made ufe of for the determination of the angles at the bafe, 

 or in any other flation whatever, where it may be neceffary ta 

 bring it very accurately over a point on the furface of the 

 ground underneath. 



'Rough meafurement of the Bfe with the Chain ^ anddetennma^ 

 tion of the relative heights of the Stations by means of the: 

 Telefcopic Spirit Level Tab. XVI. and XVIL 



Having in the preceding defcription of the '^jlhbus inft'ru- 

 ments, originally provided for the meafurement of the bafe^. 

 fully explained their conftrudlions, ufes, and modes of appli- 

 cation ; and having thereby anticipated, in a great degree 

 what muft otherwife have been faid to make them underllood 

 m any account, blended with that of the execution ; little 

 more now remains to be given than the journal of our pro- 

 ceedings from day to day, and the ultimate refult of the ope- 

 ration- 

 After a vejy tedious delay, Mr. Ramsden having at lait 

 produced his hundred- feet chain, with the portable tranfit inftru- 

 ment ; and having lent us an excellent teiefcopic fpirit levels 

 for determining the relative heights; two fedions of the bafe 

 being likewife cleared by the foldiers, and Ibme progrefs made in 

 5 the 



f 



