Trigonometrical Survey. 565 



exertion, as the triangles are branched out into several parts of 

 the kingdom. 



Were the length of a degree of the meridian, in these latitudes, 

 accurately known, the most eligible method of carrying on the 

 survey would be, that of working between any two determined 

 parallels of latitude, till the space between them was completed. 

 Yet this mode would manifestly be subject to some slight inno- 

 vations, from the necessity of measuring bases in certain stages 

 of the work : it would be right, however, to adopt the principle 

 for general practice. Under this idea, it would have been proper 

 to have commenced the operations of this year in Somersetshire, 

 and to have carried on the triangles from the neighbourhood of 

 the new base into the north of Devon. 



It is mentioned in one of the former Accounts, that a zenith 

 sector was formerly bespoken of Mr. Ramsden, by his Grace the 

 Duke of Richmond, for the purpose of aiding the design of 

 measuring the length of a degree of latitude in this country. 

 The pressure of other business caused Mr. Ramsden to lay 

 aside this instrument, after he had considerably advanced in 

 its construction. The real necessity, however, for our being sup- 

 plied with an instrument of this description being made known 

 to him, he resolved to take it in hand again, and complete it. 

 Relying on the strength of his assurances to this effect, I deter- 

 mined to relinquish the intention of proceeding to the westward ; 

 and resolved to commence this year's operations, with running 

 up a series of triangles along the meridian of Blenheim. As it is 

 probable my next communication will contain the result of this 

 interesting part of the survey, I shall now confine myself to 

 such particulars as relate to the subject under consideration. 



In a former article, I have observed, that the chief Draftsman, 



mdccc 4 D 



