Excerpt from An Elementary Text-Book of HydrostaticsIn the English system, the most usual unit of length is the foot The foot is one-third of a yard, the yard being defined as the distance between two marks on a certain bar of platinum which is now kept in the Tower of London. There is no reason why this particular length should have been chosen as the unit, beyond that of' custom. This fact is expressed by saying that the yard is a purely arbitrary unit.Smaller lengths may be measured in inches (1 foot 12 inches), longer lengths in miles (1 mile 5280 feet), both units being derived from the foot or yard.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.