We may consider in this connection the dissatisfaction of some of the greatest minds of evolutionary circles with the results of their own theory. Mr. Herbert Spencer is thus quoted, writing in his eighty-third year: "The intellectual man, who occupies the same tenement with me, tells me that I am but a piece of animated clay equipped with a nerve system and in some mysterious way connected with the big dynamo called the world; but that very soon now the circuit will be cut and I will fall into unconsciousness and nothingness. Yes I am sad, unutterbly sad, and I wish in my heart I had never heard of the intellectual man with his science, philosophy and logic." (_Facts and Comments._) Prof. Frederic Harrison, the agnostic, thus writes: "The philosophy of evolution and demonstration promised but it did not perform. It raised hopes, but it led to disappointment. It claimed to explain the world and to direct man, but it left a great blank. That blank was the field of religion, of morality, of the sanctions of deity. It left the mystery of the future as mysterious as ever and yet as imperative as ever. Whatever philosophy of nature it offered, it gave no adequate philosophy of Man. It was busy with the physiology of Humanity and propounded inconceivable and repulsive guesses about the origin of Humanity." (_North American Review_, December, 1900, p. 825.) From the opposite side of the field, President Woodrow Wilson writes: "This is the dis-service scientific study has done for us; it has given us agnosticism in the realm of philosophy, scientific anarchism in the field of politics. It has made the legislator confident that he can create and the philosopher sure that God cannot." (_Forum_, December, 1896.) UNCERTAINTY OF SCIENTIFIC THEORIES IN GENERAL. Another feature which strikes the non-scientific mind curiously is the wide differences among great scientists as to the facts of nature. The age of the earth is variously declared to be ten million years by some, and by others equally able, a thousand million years. The temperature of its interior is stated to be 1,530 degrees by one, and 350,000 degrees by another. Herschel calculated the mountains on the moon to be half a mile high, Ferguson said they were fifteen miles high. The height of the Aurora Borealis is guessed from two and a half to one hundred and sixty miles, and its nature is still more widely described. The delta at the mouth of the Mississippi was calculated by Lyell to have been 100,000 years in forming. Gen. Humphrey, of the United States survey, estimated it at 4,000 years, and M. Beaument at 1,300 years. The deposits of carbonate of lime on the floor of Kent Cavern in England have been estimated by different scientists to have been from a thousand to a million years in forming. The discovery of radium and other similar substances, it is said, is almost revolutionizing the theories of the constitution of matter and affecting all physical science.