VOL. XC.] PHILOSOPHICAL TRANSACTIONS. 701 



triangles were to rest it became certain, that their sides would depend on the 

 base on Hounslow Heath. The only means by which the series now proposed 

 to be carried westwards, for the double purpose of forwarding the survey, and 

 also of finding a portion of the meridional arc, could be properly connected with 

 the triangles in the neighbourhood of Salisbury Plain, was the side just spoken of; 

 for the high land in the vicinity of Calne, intercepted the view of the stations on 

 the Marlborough range, from White Horse Hill. In order however to make a 

 connection, though imperfect, an immediate station was chosen on this high 

 intercepting land. At Shotover Hill the party separated, each having its instru- 

 ment. This article is closed with enumerating the names of the stations visited 

 and observed, and mentioning that Shotover Hill and Cumner Hill, in Oxford- 

 shire, were selected principally with a view of ascertaining the situations of the 

 observatories at Oxford and Blenheim. The names of the stations were, Nuffield, 

 White Horse Hill, and Scutchamfly, in Berkshire. Shotover Hill, Cumner Hill, 

 Whiteham Hill, Crouch Hill, and Epwell Hill, all in Oxfordshire. Those in 

 Gloucestershire were, Pen, Cleave, Broadway Beacon, and the Malvern Hills. 

 The Lecky Hills, in Worcestershire. Corley and Nuneaton, in Warwickshire. 

 Bardon Hill, Naseby Field and Barrow Hill, in Leicestershire. Arbury Hill, and 

 Souldrop, in Northamptonshire. Quainton, Brill, Wendover, and Bow Brick- 

 hill, in Buckinghamshire. Woburn Park, and Lidlington, in Bedfordshire. 

 Kinsworth, Lillyhoe, Berkhamstead, Tharfield, and Bushy Heath, in Hertford- 

 shire. From the last mentioned station, the party returned to London, in Octo- 

 ber. A list is here added of the quantities of all the angles, at those stations, 

 taken this year 17 99 ; which is followed by a description of the situations of all 

 the stations, where the angles were observed ; by which they may be easily dis- 

 covered again, on any future occasion. 



Next follows the account of the measurement of the base, before-mentioned, 

 on Sedgemoor, including the remeasurement and adjustment of the chains. The 

 result of the whole is as follows. 



The overplus of the 273d chain was measured by Mr. Ramsden, 

 and found to be 23.517 feet; therefore the apparent length of the Feet. 



base was 27676.4S30 



From the measurement in the riding-house of the Duke of 

 Marlborough, the chain a was found to exceed 100 feet, in the 

 temperature of 54°, 0.11425 parts of an inch; to which adding the 



wear by the measurement on Salisbury Plain, viz. -^-, and also half 

 the wear by the measurement of this base, viz. — — part of an inch, 



0.1191 



we get ' for the excess of the chain's length above 100 feet; 



12 

 0.1191 



therefore --£- X 272.8 = 2.7075 feet; which add -f 2.7075 



12 



The sum of all the degrees shown by the thermometer was 985 1 1 ; 



