252 J. T. Walter— On Indian Pendulum Observations. [Nov. 
ly, while passing the proof-sheets of the volume through the press, he 
learnt the result of Captain Basevi’s observations at More ; he then made 
a calculation which showed that an assumed attenuation of matter equal to 
that of the More plateau, and extending to a depth equal to fifty times the 
height of the plateau, would, if taken account of in the reductions, leave 
so small a difference between theory and observation as to bear strong 
testimony to the truth of his hypothesis, see Art. 201. 
Archdeacon Pratt died before this edition of his Figure of the Earth 
was published. His views have since received further confirmation by the 
measurement of two longitudinal arcs across the Southern Peninsula of 
India, from Madras to Mangalore, and from Yizagapatam to Bombay. 
The terminal stations of these arcs being situated on the coast line, in each 
instance, it was probable that at each station the plumb-line would be 
deflected inland, because of the greater attraction of the land than the sea, 
in which case the astronomical amplitudes would have been greater than 
' the geodetic. Actually, however, the converse was found to have happened, 
for the astronomical amplitudes proved to be less than the geodetic ; this 
showed that the plumb-line had been deflected towards the sea, presumably 
because of denser matter under the bed of the ocean than under the 
land. 
An additional support to the Archdeacon’s hypothesis has been recent¬ 
ly furnished by an interesting calculation in Colonel Clarke’s latest investi¬ 
gation of the Figure of the Earth, published in the Philosophical Magazine 
for August, 1878. Colonel Clarke has computed the departure (in a 
vertical plane) of the curve which best represents the Indian meridian, on 
the evidence of the geodetic observations in India, from the curve which 
best represents the earth as a whole, on the evidence of the geodetic obser¬ 
vations in all other parts of the world as well as India. He shows that 
the curves cross each other, and that their departure in no case exceeds 20 
feet ; and he says—“ This deformation may or may not be due to Hima- 
“ layan attraction ; at any rate we have here an indication that that vast 
“ table-land does not produce the disturbance that might a priori have 
“ been anticipated. This is in accordance with the fact that there is an 
“attraction sea-wards at Mangalore and Madras, and slightly also at 
“ Bombay : and I think we have here a corroboration of Archdeacon Pratt’s 
“ theory, that where the crust of the earth is thickest there it is least 
‘‘dense ; and where thinnest, as in ocean-beds, there it is most dense.” 
If the hypothesis of sub-continental attenuation and sub-oceanic con¬ 
densation is a true one, and is in accordance with the actual facts of the 
constitution of the earth’s crust, then it follows that there can be no very 
