So far as the practical man is concerned, he is not, as a rule, particularly interested in abstruse speculations about the nature and constitution of matter, nor even in the details of planetary evolution. He is more interested in the nature and constitution of the earth, his dwelling-place, and as a consequence Geology is more popular than Physics. In this department of science Scotland has done brilliant work. The study of the earth entered the scientific stage when James Hutton published his epoch-making book. His book The Theory of the Earth has been described by Huxley as one of "the most remarkable contributions to geology which is recorded in the annals of the science." It was remarkable in this, that it applied, for the first time, scientific method to a subject which had been relegated to the realm of speculation. When Hutton began to study the earth geologically, the crudest notions prevailed. The great changes everywhere apparent were associated with the Deluge. Other theories were afloat, but being merely speculative they possessed no scientific value. The question which Hutton faced was this—by what agencies had the earth been sculptured into its present form ? According to one theory—the catastrophic—the principal agencies at work were convulsions, cataclysms, fire and flood. Hutton opposed this with the theory of uniformity, which meant that we must seek geological interpretation in causes which we observe operating in the present, and exhaust them before we import causes which no longer exist. As the result of prolonged study, Hutton came to the conclusion that the earth, instead of being a rigid mass, is everywhere undergoing changes. Slowly but surely the hardest rocks are being disintegrated by atmospheric, mechanical and chemical agencies. In addition, the oceans are perpetually eating in upon the land. Let this process continue long enough, and, argued Hutton, entire continents will be worn away.

What then? With the wearing away of the continents the oceans are filled up. The solidifying of the debris at the bottom of the oceans gives rise to new rocks, which become the basis of new continents. To Hutton it seemed clear "that the basis of the present continents was laid in ancient sea-beds formed of the detritus of continents yet more ancient."

An important question arises—by what agency were these rocks lifted above the oceans so as to form new continents? Hutton's reply was subterranean heat, which in the form of volcanic action upheaved ocean beds to form continents. This theory, to which Hutton, after many years' silent study, gave publicity in 1785 in a paper to the Royal Society of Edinburgh, met with violent opposition. A rival school, headed by Werner, a German, repudiated the volcanic part of the theory, and relied upon what is known as the aqueous theory. Over these two theories a violent controversy long raged. The Huttonians were known as Plutonists, while the followers of Werner were described as Neptunists.

It is a remarkable tribute to the thoroughness of Hutton's investigations that later students in the same field have found little to add to this enumeration of agencies in earth changes. In his Theory of the Earth, published in 1788, Hutton notes the following agencies—degradation of land by atmospheric and aqueous agencies, deposition of the debris as sediment in the ocean, consolidation and metamorphosis of sedimentary deposits by the internal heat and by injection of molten rock, disturbance and upheaval of oceanic deposits and formation of rocks by the consolidation of molten material, both at the surface and in the interior of the earth. Comparing this, remarks Professor Arthur Thomson, with Professor Geikie's book, Earth Sculpture, it is seen that only a few "additional modes of operation have been discovered in the course of the century. The progress has been in measuring the efficiency of the factors which Hutton recognized, rather than in discovering new ones."

To Hutton belongs the credit of placing geology on something like a scientific basis. His theory of the earth's formation, sound at heart, contained, however, serious imperfections, with which it was the work of another Scotsman, Sir Charles Lyell, effectively to deal. Hutton was right in attributing great geological changes to volcanic action, but his conception of the work of that agency was erroneous. He supposed that after long intervals of quietness volcanic action suddenly shot up great continents. What Lyell did was logically to apply Hutton's own theory of gradual changes to the entire geological phenomena. He denied the existence of great violent upheavals, and contended that the phenomena of the past were explainable on the theory of gradual changes. Lyell pinned his faith not merely to the uniformity of nature, but also to the marvellous effects of gradual changes extending over long periods of time. Phenomena which the Hutton school thought could only be produced by volcanic eruptions were traced by Lyell to the slow action of warmth, frost and rain. Lyell, however, had not exhausted all the causes of the earth's changes. It began to be seen that among the causes was ice, and after much controversy the existence of a great Ice Age was admitted, the influence of which had to be added to the agents mentioned by Lyell as a factor in sculpturing the earth, so to speak, into its present shape.

Sir Charles Lyell's merits have long been recognized. On the foundation laid by Hutton he erected a solid and imposing structure. No less an authority than Darwin has left on record these words: "The science of geology is enormously indebted to Lyell—more so, I believe, than to any other man who ever lived."

In Geology as in Physics the Scottish school, has well maintained its best traditions by contributing greatly to the remarkable advance of the science during the nineteenth century. Among those who conspicuously contributed to this advance Sir Roderick Murchison deserves special mention. By his explorations among what are known as the Transition rocks he added a new chapter to geological science. Sir Archibald Geikie states in his book The Founders of Geology that Murchison's four months' labour among the Transition rocks marked a new step in British geology. It was the first successful foray into these hitherto intractable masses, and prepared the way for all that has since been done in deciphering the history of the most ancient fossiliferous formations alike in the Old World and the New. At the end of seven years' toil Murchison published his monumental work The Silurian System, which forms "a notable epoch in the history of modern geology and entitles its author to be enrolled among the founders of the science."

Coming to later times the science is admirably represented in Scotland by Sir Archibald Geikie and Professor James Geikie, who, with the advantage of being able to apply the fruitful idea of evolution to geology, have been able to weld into an organic whole the scattered discoveries of the past and the present. In one department, that of glaciation, Professor James Geikie's The Great Ice Age is recognized as a crowning work of the nineteenth century. Special mention must be made of Hugh Miller, who, in addition to original research, will always be remembered as the popularizer of the science just when it was in danger of being buried in the debris of technical terms.

Turning to the more complex science of organic nature, we find Scottish scientists of the eighteenth century doing excellent work. There is, for instance, William Cullen, who, as professor of medicine at Glasgow and afterwards in Edinburgh, gave a marked impetus to scientific knowledge in more than one department. His biographer claims for him that his investigations into heat and cold must not only have directed the attention of his pupil Black to these studies, but must also have furnished him with several of the data for his profound reflections on latent heat. Be that as it may, Cullen, though unduly speculative in his method, made important contributions to the science of medicine. It is claimed that "to him is largely due the recognition of the important part played by the nervous system in health and disease." Many of his speculations "as to the reflex nervous action of sensory and motor fibres, and the connection of sensory and motor fibres, are accepted facts."

The name of Cullen, whose fame rests on his contributions to pathology, suggests the name of John Hunter, who was equally at home in physiology and pathology. Hunter's mind was distinguished by two qualities not often found together—great comprehensiveness of outlook and patient attention to detail.

He had quite a Spencerian passion for width of view, and for the accumulation of facts. Hunter had grasped the modern idea of the continuity of Nature perhaps better than any of his contemporaries. At any rate he made it the guiding idea in his investigations. For instance, in treating of the human body he declared it to be necessary to proceed by the aid of principles derived from a study of animals whose laws again must be studied through the laws of inorganic matter. Quite in the spirit of the evolution theory, Hunter desired to unite all branches of physical science in the order of their development, proceeding from the simple to the complex. His passion for facts saved him from the danger of losing himself in pure speculation. His researches, we are told, covered the whole range of the animal kingdom. He dissected upwards of five hundred different species, exclusive of his dissection of a large number of plants. At the time of his death his museum contained upwards of ten thousand specimens illustrative of human and comparative anatomy, physiology, pathology and natural history. So valuable was the collection that it was purchased by the Government for £15,000, and presented to the Royal College of Surgeons.

When we come to other sciences, we find Scotsmen taking leading positions. In physiology how much do we owe to Sir Charles Bell's pregnant ideas on the nervous system ! In 1811 Bell published privately a pamphlet setting forth a "New Idea," in which he stated the opinion that " the nerves are not single nerves, possessing various powers, but bundles of different nerves, whose filaments are united for the convenience of distribution, but which are distinct in office as they are in origin from the brain." The value of this pamphlet is shown by the remark of Sir Michael Foster that "our present knowledge of the nervous system is to a large extent only an exemplification and expansion of Charles Bell's ' New Idea,' and has its origins in that."

In what is called cellular physiology, important contributions were made by Professor John Goodsir and his brother. In this department John Goodsir—whose name in the history of science, particularly with reference to the cell-theory, has strangely been allowed to fall into the background—was a pioneer. In 1842 he communicated to the Royal Society of Edinburgh a paper on secreting structures in which he established the principle that cells are the ultimate secreting agents. In the cells of the liver, kidney, and other organs he recognized the characteristic secretion of each gland. The secretion, he said, was situated between the nucleus and the cell wall. At first he thought the secretion was formed by the agency of the cell wall, but later he regarded it as the product of the nucleus. Full justice in science books has been done to the labours in this connection of Schleiden, Schwann and Virchow, but Scotland's share in the formulation of the cell-doctrine, as represented by Professor John Goodsir, has not had adequate recognition.

In other branches of physiology Scotsmen have done notable work. In embryology Professor Arthur Thomson—who himself deserves honourable mention along with Professor Geddes in the present generation—links the name of Francis Balfour with that of Von Baer, and states that Balfour's monumental text-book (1880-1881) gave a strong stimulus to the study of biology.

In the larger sphere of biology, that dealing with the origin of species, Scotland has done lasting work. To thinkers of a scientific cast of mind the special creation theory presented great difficulties, and Leslie, as we saw, groped his way to the evolutionary conception that Nature in all her productions "exhibits a chain of perpetual gradations, and that the systematic divisions and limitations are entirely artificial, designed merely to assist the memory and facilitate our conceptions." The evolutionary idea remained in the air, though Lamarck's views now and again cropped up in biological literature. It was not till 1830 that in the persons of distinguished French scientists the creation and the evolutionary theories came into collision at the memorable debate at the Academy of Sciences between Cuvier and Geoffrey Saint-Hilaire. Cuvier clung to the old view, and St. Hilaire contended for the theory of the transmutation of species. Cuvier was believed to have inflicted a crushing defeat upon his rival, and for a time there was a lull in the controversy. In 1844 appeared the Vestiges of Creation, by Robert Chambers, and the controversy raged with redoubled fury. Of course Darwin's epoch-making book superseded all previous attempts to solve the problem. For his pioneering labours in this department Chambers, however, deserves to be held in lasting remembrance. In Germany the problem had been attacked from the side of philosophy, but the speculative methods of Oken, Schelling and Hegel bore no fruit, simply from the absence of scientific method. Chambers attacked the problem on scientific lines. Darwin acknowledged the great value of the book; and perusing it in the light of modern knowledge the student cannot fail to be impressed with the masterly manner in which Chambers surveys the whole field, and marshals his facts in support of the developmental theory. As he puts it, just as the inorganic world had been reduced to unity by one comprehensive law—Gravitation, so in the organic world one all-comprehensive law reigns— Development. It is difficult at this time of day to realize the storm which arose over the Vestiges. Science joined hands with theology in denouncing the book, the leading conception of which outlived all attack and found its appropriate setting in the far-reaching, luminous generalization of Darwin.

Strictly speaking, science has discharged its task when it discovers and unifies the laws of phenomena. But the mind of man refuses to rest in phenomena. Beyond the relative it seeks the absolute, and almost unconsciously science encroaches upon philosophy and religion. Living habitually in the world of the concrete, men of science when they go beyond descriptions to explanations of phenomena have a tendency to rest in materialistic views of the world.

Forty years ago it seemed as if philosophy had received its death-blow at the hand of science. George Henry Lewes wrote a history of philosophy with the avowed object of showing that it was mainly a record of futile strivings, of wasted efforts. Science, with its atoms, its molecules, its ether, had taken up the great problems of the Universe and, it was believed, was competent to present a coherent set of intelligible explanations resting on the bed-rock of experience. Science laid claim to have got down to reality, whereas philosophical speculations were supposed to be a kind of bottled moonshine. By and by speculative thinkers began to ask, What is this Reality about which men of science talk so glibly? Science does not talk quite so glibly now, though even yet the old dogmatic note is heard. Men like Haeckel in Germany, and distinguished speakers at British Association meetings, talk about the Universe and its constitution in terms of Matter and Energy as if these terms were fundamental and exhaustive, instead of being symbolical and provisional. It can be claimed for the Scottish school that its distinguished members have refused to coquet with materialism, and in regard to the ultimate problems God, the world and man, have been in close agreement with religion and philosophy. Striking evidence of this is furnished by the suggestive book, The Unseen Universe, by the distinguished Scottish scientists of their day, Messrs. Balfour Stewart and Tait. However much the Scottish scientists of the eighteenth century were opposed to the rigid Calvinism of their time, their deistic mode of thought kept them free of materialism, which extensivelv prevailed in France, and which in our day has found expression in the writings of English and German men of science. In its interpretation of science philosophy in Scotland has consistently opposed materialism. Professor Pringle Pattison fitly represents the attitude of the Scottish school when he dwells upon the futility of all attempts " to explain human life in terms of the merely animal, to explain life in terms of the inorganic, and ultimately to find a sufficient formula for the cosmic process in terms of the redistribution of Matter and Motion." Thanks to the effective philosophical criticism of thinkers like Professor Pringle Pattison, a great change has come over scientists. The more thoughtful no longer mistake their descriptions of phenomena for explanations, and acknowledge that the mystery of the Universe lies beyond the reach of their mechanical categories. It is now being recognized by the rising generation of scientists that all attempts to convert atoms, ether, or energy, into ultimates, end in futility. Nothing could bring into clearer light the victorious nature of Professor Pringle Pattison's battle with materialism than the following admission by a brilliant Scottish scientist who is rapidly coming to the front, Professor Arthur Thomson, who thus refers to the inevitable limitations of the mechanical explanations of things: "When we consider any particular corner in the inanimate world, say the making of the Niagara Falls, or the making of the frost flowers on the window, we do not require in our redescription more than mechanical formulae; but when we consider Nature, not in isolated pieces, but as a harmonious whole, the progressive order, the orderly progress, and the beauty of it all, when we go on to recognize that the earth has been the parent of its tenants, then we must read back into the world-egg with which we start a potentiality of giving rise to all that follows." What is this but saying in the language of science, what Professor Pringle Pattison says in the language of philosophy, that "if the Universe is one, we have to read back the nature of the latest consequent into the remotest antecedent."

So long as the materialist view of Nature prevailed, so long as the great Cosmic processes were conceived in terms of mechanics, the feeling of wonder and the sense of mystery were repressed. It is now admitted that vital processes such as the phenomena of life cannot be expressed in terms of physics and chemistry, and that between the physics of the brain and consciousness there is a great gulf fixed. Scientists are coming to see that the philosophers were right who contended that Nature should be interpreted through man, rather than man through Nature. Science has severe limitations, to which the leaders of to-day are keenly-alive. In their writings there is none of the crude philosophy and boastfulness which characterized the writings of the materialists of the mid-nineteenth century. The difference is well marked in the following passage from Professor Arthur Thomson's Bible of Nature: "It is the work of science to reduce things to a common denominator or to a simple beginning, such as matter, energy and ether, or the life of a protoplast. This sort of analysis and genetic description clears up obscurities, affords a basis for action, and is in any case forced upon us by our desire to unravel things to refund phenomena into their antecedent conditions. But it does not satisfy the human spirit, partly because the common denominator is in itself mysterious, partly because science never tells us why so much should come out of apparently little." What is the conclusion of the whole matter? In the words of Professor Thomson: "Many scientific thinkers who can find no resting-place in science alone agree with the author of the Foundations of Belief (Mr. Balfour) when he says: 'I do not believe that any escape from these perplexities is possible unless we are prepared to bring to the study of the world the presupposition that it was the work of a rational being who made it intelligible, and at the same time made us, in however feeble a fashion, able to understand it.'" Interpret man through Nature, as the leading scientists of a former generation did, and you bind humanity fast in fate and deprive life of all rational purpose. Interpret Nature through man, after the manner of the new school of scientists, and you make possible the view that through the ages an increasing purpose runs, and that the highest instincts of the soul are not delusive by-products, but prophetic hints of a life that will bloom and blossom otherwhere.

Science when philosophically interpreted leads the mind into the region of religion. In the words of John Fiske, one of the most brilliant expounders of science from the evolutionary standpoint—