Note 6 — Chapter 15
Reading edition
"It has been calculated that at the depth of 35 miles, air, subjected to the pressure of a column of matter of the mean density of that at the surface of the earth, would acquire the density of water; that at the depth of 173 miles, water itself, which is eminently incompressible, would acquire the density of marble; and at the centre, marble would have a density 119 times greater than at the surface. But the comparatively small mean density of the mass [of the earth] proves that none of these effects take place."—Brande.