In 1885, before Keely's scientific explorations had taught him that no engine can ever be constructed by which the ether can be used and controlled, as we now use and control steam, he wrote, in a letter to a friend, "I shall not forestall an unproved conclusion, but fight step by step the dark paths I am exploring, knowing that, should I succeed in proving one single fact in science heretofore unknown, I shall in so doing be rewarded in the highest degree. In whatever direction the human mind travels it comes quickly to a boundary line which it cannot pass. There is a knowable field of research, bordered by an unknown tract. My experience teaches me how narrow is the strip of territory which belongs to the knowable, how very small the portion that has been traversed and taken possession of. The further we traverse this unknown territory, the stronger will become our faith in the immovable order of the world; for, at each advancing step, we find fresh fruits of the immutable laws that reign over all things,--from the falling apple, up to the thoughts, the words, the deeds, the will of man: and we find these laws irreversible and eternal, order and method reigning throughout the universe. Some details of this universal method have been worked up, and we know them by the names of 'gravitation,' 'chemical affinity,' 'nerve-power,' &c. These material certainties are as sacred as moral certainties.... The nearest approach to a certainty is made through harmony with nature's laws. The surest media are those which nature has laid out in her wonderful workings. The man who deviates from these paths will suffer the penalty of a defeat, as is seen in the record of 'perpetual motion' seekers. I have been classed with such dreamers; but I find consolation in the thought that it is only by those men who are utterly ignorant of the great and marvellous truths which I have devoted my life to demonstrate and to bring within reach of all. I believe the time is near at hand when the principles of etheric evolution will be established, and when the world will be eager to recognize and accept a system that will certainly create a revolution for the highest benefits of mankind, inaugurating an era undreamed of by those who are now ignorant of the existence of this etheric force." These views which have guided Keely in all his researches cannot be made known to any just, discerning mind without an accompanying perception of the gross way in which he has been misrepresented by his defamers; as well as some appreciation of the scientifically cautious manner in which he has pursued his investigations, since he abandoned his efforts to construct an engine that would hold the ether in rotation.