115 



greater than it is given by the Astronomer Royal in his ' Figure of 

 the Earth,' and that the ellipticity is yfiaa* or as the Astronomer 

 Royal conjectured, something " greater than i," which he gives in 

 the same paper. 



The mean specific gravity of the earth, as derived from the obser- 

 vations at Arthur's Seat, was stated in a former paper to be 5-14 ; 

 the calculations have since been revised, and it is now found to be 

 5-316. 



The mean specific gravity of the earth, as derived from the only 

 other observations on the attraction of mountain masses on which 

 any reliance has been placed, viz. the Schehallien observations, is, as 

 finally corrected by Hutton, ^, or almost 5'0. 



From the experiments with balls we have the following results : 

 By Cavendish, as corrected by Baily. . . . 5 '448 



By Baily 5'67 



By Reich 5'44 



From the pendulum experiments, at a great depth and on the 

 surface, the Astronomer Royal obtained 6*566. 



Two copies of the new National Standard Yard have recently been 

 received through the Astronomer Royal, and it is obviously neces- 

 sary that the geodetic measures should be given in reference to the 

 standard ; but not knowing from what scale the standard has been 

 taken, Col. James is unable to say at present in what way the re- 

 duction is to be made ; that is, whether by reference to the compa- 

 rison of the old standards which have been already made, or by the 

 mechanical process of a direct comparison of the Ordnance Standard 

 with the new National Standard. 



This introductory explanation by Col. James is followed by an 

 account of the Trigonometrical operations and calculations ; the fol- 

 lowing is a brief statement of the results : 



" 1st. The four bases of verification, when their measured lengths 

 are compared with their lengths as calculated from a mean of the 

 Lough Foyle and Salisbury Plain bases, show the following discre- 

 pancies : 



Hounslow. I Mistcrton Carr. 



+ 0-173 -0-157 



Rhuddlan Marsh. 

 + 1-596 



Belhelvie. 

 + 0-240 



