Note 10 — Chapter I · EVOLUTION OF ATLANTIC TELEGRAPHY IN AMERICA AND ENGLAND
Reading edition
In the present day, however, soundings are taken at intervals of about ten miles along the proposed route, and even then submarine hills and valleys are frequently encountered. This is effected by means of the Thomson steam sounding-apparatus, the great feature of which is a fine steel wire (the same as that in the treble notes of a piano) in place of a hempen line of enormous bulk. Nowadays, taking a sounding in the Atlantic occupies well under an hour of time, where by the old method it took at least six hours.