of the Acceleration of Gravity for Tokio, Japan. 49 



use made of all trustworthy pendulum-observation is to deter- 

 mine the constants of Clairault's formula. 



IV. Major Herschel criticises the statement in our paper, 

 " Captain Clarke has found that the equator is elliptical," says 

 that it is wrong, and that it should be : — " What he [Captain 

 Clarke] has taught is in effect this : Assuming an equator 

 more or less elliptical, the ellipticity seems to be such-and-such ; 

 but this is not to be taken as any proof of such ellipticity." But 

 here again, on the other hand, our statement was made on 

 good authority ; for in ' Comparisons of the Standards of 

 Length of England, France, Belgium, Prussia, Bussia, India, 

 Australia, made at the Ordnance Survey Office, Southampton,' 

 by Captain A. R. Clarke, B.E., under the direction of Colonel 

 Sir Henry James, R.E., F.R.S., published by order of the 

 Secretary of State for War (1866), we find : — " In computing 

 the figures of the meridians and of the equator for the several 

 measured arcs of meridian, it is found that the equator is 

 slightly elliptical, having the longer diameter of the ellipse in 

 15° 34"' East longitude." 



Surely this is as much a proof that the equator is elliptical 

 as is Newton's proof that the planets attract one another accord- 

 ing to a particular law because such a law of attraction would 

 explain the planetary motions. But the reason for this attack 

 of Major Herschel's on our statement that Captain Clarke had 

 found the equator to be elliptical is seen from a passage in 

 his article in 'Nature ' on Colonel Clarke's ' Geodesy.' There 

 Major Herschel admits that " unhappily" his " attitude " is 

 a "prejudiced " one, because, he says : — "We have regarded 

 the earth, mentally, for so many years as an irregular spheroid, 

 and all ellipsoids or other mathematically simple figures as 

 mere conveniences, that we cannot bring to bear upon the 

 exact determination of any particular one of these that intense 

 curiosity which is necessary to sustain one in the search for 

 the most probable." This is, of course, quite consistent with 

 the practical man's well-known rule of working, not to 

 trouble his head with " mathematical labyrinths," nor with 

 " the method of potentials," nor to countenance as " a legiti- 

 mate part of geodetical study " calculations of rise of sea-level 

 due to submerged spheres of rocky matter, and the like, which 

 Colonel Clarke seems to have been so guilty as to do. 



In i Nature ' Major Herschel is annoyed that Colonel Clarke 

 should have spoken of the method of coincidences as modern; 

 and he is more angry when we do so. Colonel Clarke was 

 in his treatise compelled to leave out part of the history of his 

 subject; and Major Herschel says: — "It is impossible not to feel 

 surprise that the existence even of the enormous body of work 



Phil Mag. S. 5, Vol. 10, No, 59. July 1880. E 



