The earliest records of the employment of some artificial means for sending the ship along are not preserved to us, although it is certain that repeated attempts were made in many ages to do without oars and sails. When slave labour was cheap and plentiful, and this could easily be turned into propelling power, perhaps it was hardly likely that there would be much incentive for discovering or rediscovering such forces as steam to do the work of physical energy. It seems to me to be a curious and interesting fact that it was not until the freedom of the individual from some sort of slavery and servitude--whether belonging to ancient times or the Middle Ages--began to be asserted that there was any real progress made in labour-saving devices. The dignity of man, and his superiority as a being possessed of intelligence and discernment, and, consequently, his right to be considered as something more than a drawer of water, a hewer of wood, and the motive force for any method of transport, had fully to be recognised and appreciated before means were earnestly sought to save human labour. The cry of the last few years and the tendency exhibited by many world movements have been all for asserting the right of the individual. The French Revolution, the American War of Independence, the rise of Socialism of some sort or another in most civilised countries, have happened collaterally with the progress of machinery, and the development of power independent of physical force, necessitating less and less the expenditure of human energy. Never in the history of the world has so much been accomplished for obtaining mechanical energy as within the last hundred and fifty years, and never perhaps has the individual been able to possess himself of so much freedom.