Sir John Leslie observes, that _air compressed_ into the fiftieth
part of its volume has its elasticity fifty times augmented: if it
continued to contract at that rate, it would, from its own incumbent
weight, acquire the density of water at the depth of thirty-four
miles. But water itself would have its density doubled at the depth
of ninety-three miles, and would attain the density of quicksilver at
the depth of 362 miles. In descending, therefore, towards the centre,
through nearly 4000 miles, the condensation of ordinary substances
would surpass the utmost powers of conception. Dr. Young says, that
steel would be compressed into one-fourth, and stone into one-eighth,
of its bulk at the earth’s centre.--_Mrs. Somerville._