55^ The Account of a 



place of the great one, and was used, with good effect, in carry- 

 ing on the subsequent operations in this quarter. 



In our Paper published in the Philosophical Transactions for 

 1795, an observation is made, of the necessity then existing for 

 the measurement of a base on Salisbury Plain, in consequence of 

 resolutions taken to inclose Sedgemoor : an act for which pur- 

 pose was passed a few years ago, and partly carried into execu- 

 tion in 1797. At this time, however, King's Sedgemoor was only 

 set out into parochial allotments, as exhibited in Plate XXVIII. 

 accompanying this Account. The ditches, represented by lines on 

 this plan, were generally ten feet broad, and five feet deep ; but the 

 principal and secondary drains were much wider, the first being 

 thirty, and the last twenty-five, feet in breadth . The subdivisions 

 on the Moor, or the individual allotments of it, were not traced 

 out in the Somerton quarter, at this time, the task being deferred 

 till the latter part of the following year. The measurement, 

 therefore, of this base, in an early part of the season, became 

 necessary, because fewer obstacles were then expected to present 

 themselves. 



As it appeared that many instances would probably occur, in 

 which a chain of 50 feet in length would be useful, if not abso- 

 lutely necessary, one was provided by Mr. Ramsden, in the 

 winter ; its. make and form being precisely similar to those of 

 the larger chains, used in the measurement of our former bases. 

 Such a chain did, indeed, prove highly serviceable in the subse- 

 quent operation; as the handles of the 100-feet chain would 

 very often have had their places in ditches, or been so situated 

 on their banks, as to leave imperfect means of correctly placing 

 the register heads under the handles. ' • 



The apparatus for the measurement, consisting of the tressels 



