464 et Hetbiessy on the Interior of the Earth. 
forming to the observed properties of fluids, both Sir William 
Thomson and Mr. Darwin have applied their great powers as 
accomplished mathematicians to the tides of an incompressible 
and homogeneous spheroid, such as I admit to have no real 
existence whatsoever. 
4. The labor bestowed on the problem investigated could 
scarcely be considered at all necessary or fruitful, except as 
affording an admirable illustration of the results flowing from 
the employment of hypotheses framed in direct contradiction 
to the fundamental conditions to which every truly philosophi- 
cal hypothesis must conform. It is scarcely necessary to add, 
that the conclusions of Mr. Darwin, as well as those of Sir Wil- 
liam Thomson, cannot be considered as having invalidated the 
carefully framed hypothesis that the earth consists of a solid 
crust physically similar to the rocks we are enabled to observe, 
and a contained spheroid of liquids and physically similar to 
the liquid rock poured out by volcanic openings. 
. It is with much satisfaction that I can trace a gradual 
growth of more correct physical views on the questions referred 
to in this paper. In Nature, vol. v, p. 288, a paper appeared 
in which I ventured to criticise Sir William Thomson's memoir 
on the Rigidity of the Earth, in the Philosophical Transactions. 
At the Meeting of the British Association in Glasgow, Sir Wil- 
liam Thomson acknowledged the invalidity of many of his 
of the earth. He forgot that an idea may not be the less true 
because it is sensational. The idea of antipodes was at one 
time regarded as highly sensational. Those who witness @ 
great earthquake or volcanic eruption are usually impressed 
with the sensational character of the phenomena. 
_6. A traveller who was in Portugal more than forty years 
since, met a woman over one hundred years of age, an asked 
