"of the relative lengths of the ages and periods, or their time-ratios," and says "future discovery will probably enable the geologist to determine these ratios with far greater certainty and precision. Although geology has no means of substituting positive lengths of time in place of such ratios, it affords facts sufficient to prove the general proposition that Time is long." This "proof" we hold as demonstration; and the substitution of "relative lengths of ages and periods" for "positive lengths of time" certainly justifies the use of the term "incalculable" as applied to them.
We had said that "it is a demonstrated truth of Nature that matter is indestructible," and Dr. Deems asks: "When, where, and how, was this ever 'demonstrated?' Even if it be true that matter is indestructible, can it be demonstrated? Dare any but an infinite intellect make such an assertion?" It was a theory held for thousands of years that, in the workings of Nature, matter is constantly created and destroyed—comes out of nothing and goes back to nothing. Modern science brought this theory to the test of experiment, and showed that it was erroneous. No facts were found to sustain it, but, on the contrary, all the facts prove the truth of the opposite theory, that the changes of matter are changes of form, and that matter itself is indestructible. A theory is demonstrated when all the facts verify it. Every experiment and observation in the whole body of science, physical and chemical; every fact, induction, and deduction, reached by the human mind, confirms the truth of the indestructibility of matter, and there is no shadow of evidence against it. What is this but a demonstration? And, if the proposition is sustained by this high degree of proof, we fail to see what there is of "daring" in giving it a label that expresses the fact.
There remains another important point suggested by a question of Dr. Deems, which, for want of space, we put over to next month.
Prof. Morse has been quietly delivering a course of four lectures, in the large hall of the Cooper Institute in this city, on "Evolution." We say quietly, because there has not been much said about them by the press, as they have been given in the admirable series of free Saturday evening lectures that run through the season, and have become matters of course with the lecture-going public. Yet these lectures of Morse's might well have attracted the prominent attention of our newspapers, as they were unequaled in the skillful presentation of biological facts and principles commonly dry and forbidding, so as to be perfectly understood and intensely relished by large audiences of non-scientific people. Prof. Morse has remarkable gifts as a lecturer, and in the field of science is without a peer on the American platform. In the first place, he knows his subject thoroughly, and is charged to overflowing with its latest and freshest facts and illustrations. In the second place, he has a faculty of rapid and accurate delineation of the forms and structures of life that he is dealing with, that is unique and unapproachable by any other man that we ever saw work with the blackboard. He chalks as fast as he talks, and while he talks, and without spoiling his talking; and by his marvelous creations he holds his auditors as closely through their eyes as their ears. His manner as a speaker is, moreover, free, colloquial, spirited, and impressive, and his utterances vigorous, pointed, and racy. These arts are, however, all subordinate to the solid work of instruction. The last lecture of his course, although dealing apparently with technical and formidable scientific facts concerning the relations of