The universe Ptolemy saw was different from that of Copernicus, and Newton's different from both, so my conception of the universe is different from that of Prof. Newcomb's. Imagination is a creature of education and converts knowledge into utility, and reasons from the known to the unknown, and is the telescope of futurity and the microscope of past centuries. I am a great believer in imagination or ideality as the highest gift of Deity, and accept Napoleon's statement that "imagination rules the world." I believe no man can be a great astronomer without it, and the tallest and broadest enlightened imagination will naturally have the best conception of the complicated motion and grandeur of the universe. Tyndall in an address at Liverpool in 1870, said, "There are tories even in science who regard imagination as a faculty to be feared and avoided rather than to be employed. In fact, without this power our knowledge of nature would be a mere tabulation of coexistence and sequences; the soul of force would be dislodged from our universe; casual relations would disappear, and with them that science which binds the facts of nature to an organic whole." This is nobly and truly said, for all progress is heralded by theorization; which is an intelligible explanation of things, and serves to relate cause and effect. It distinguishes the human being from the animal, the civilized from the savage, the wise and learned from the ignorant and foolish. Herbert Spencer said, "In the formation of a theory we have the highest condition of the human mind." And Holder, in his life of Darwin, says, "Darwin was greater than others, because he had the genius of scientific hypothesis." Therefore I am proud of Prof. Newcomb's hypothesis of the cause and manner of the death of the solar system, though I do not accept his theory or his conclusions. I am glad he is not one of those scientists, who said in the New York Journal not long ago, that the only thing of value to science was the tabulation of facts. The mere tabulation of facts would be of as little value to the world without causation, theory and hypothesis, as the Egyptian hieroglyphics before the discovery of the Rosetta Stone. Let us see what the learned astronomer, Prof. Newcomb, says. He projects himself into the future and starts out by imagining that from the central observatory in the Himalayas, "Mars is signalling a dark star." This, he says, was after "the world had long been dull and stagnant." Now, I protest that this world will never become dull and stagnant, nor any part of this electric universe, but all will go on steadily progressing to more perfect conditions. Here is where our theories clash on the first sentence.