The overpowering belief that this world alone sustained creatures of intelligence formed an obstructive barrier to any and all attempts made to uphold--at least by analogy--the idea of intelligence in other worlds. One cannot but regret that some philosopher had not, years before Schiaparelli's time, expressed the conviction that Mars might perhaps be more favorable to the existence of intelligent life than our own world, and with this conviction proceed to formulate the conditions which must of necessity exist: namely, that the planet being a much older world than ours, its waters had mostly vanished by chemical combination with the rocks and otherwise. Following this assumption, the philosopher might have insisted that in the last extremity the melting snow caps would be utilized by the supposed intelligences to furnish water for potable and irrigating purposes. The philosopher might have superadded to this idea the prediction that, when telescopes were strong enough and eyes were keen enough, evidence of the truth of this supposition would be found in canals of some sort and that such lines should be carefully sought for. Fancy the exultation of Schiaparelli when at last he found the lines precisely as indicated. Such an announcement from so distinguished an astronomer would have been hailed with acclaim. Alas! for the conservatism of astronomers, such powers of prevision are sadly wanting. Le Verrier's prediction of an outer planet was a matter of dead certainty. The perturbations of Uranus could not be accounted for except by the assumption of an outside body, and had it not been for the characteristic reserve of English astronomers, Adams might have had the full credit. So rare are predictions of this nature in the history of astronomy that this instance will probably be quoted to the end of time. The masses, still ignorant of the certainty of mathematical astronomy, regard the prediction of an eclipse as in the nature of a prophecy. The liberal attitude of naturalists stands in marked contrast, and the history of their work is filled with examples of prediction and repeated confirmations. Until the middle of the last century--grounded in the belief of special creation--how wonderfully rapid was the conversion of naturalists to the theory of evolution after Darwin had offered his rational views on the subject. The existence of forms was predicted, based on the idea of evolution, and these have been found again and again. Our museums display in their cases remains of fossil animals which complete many series undreamed of in pre-Darwinian days. This wonderful work has been accomplished without resort to algebraic formulæ, and yet when mathematics can be applied, as it is in the law of variation, quantitative studies in heredity, and statistical methods generally, it is promptly seized upon by the biologist. * * * * *