The Eloquence of the Month.

WM. R. GROVE, Q.C., F.R.S., ON CONTINUITY IN SCIENTIFIC RESEARCH AND DISCOVERY.

[WM. R. GROVE was born at Swansea, 14th July, 1811, and educated in the Royal Grammar School there, and at Oxford, where he graduated, 1835. In November of the same year he was called to the bar as a member of Lincoln's Inn. He is attached to the South Wales Circuit, and is as well known as a barrister as a man of science. His earliest celebrity was gained as an Electrician. In 1839 his paper "On a New Voltaic Combination was read in the Royal Academy of Sciences of Paris; and an account of this new nitric acid (now called Grove's) battery appeared in the Philosophical Magazine. In 1841 Mr. Grove was appointed Professor of Experimental Philosophy in the London Institution as colleague to Faraday. That year, in his lectures, he epitomized the scientific discoveries made since the inauguration of that institution in 1819. This account the directors published. He also lectured on his new battery, and on magnetism. In 1842 he illustrated "The Physical Elements of the Ancient Philosophers," and lectured on Light. In 1843 he lectured on Attraction, and "On the Correlation of Physical Forces." The latter lectures were printed at the request of the Directors of the London Institute, as a substantive work, though only for private circulation. On these and cognate subjects he prelected, experimented, and wrote, until in 1846, from pressure of other duties, he resigned his chair. The Royal Society medal was voted to him in 1847, for papers on Voltaism; and in the same year he delivered the Baker Lecture (founded by the son-in-law of Daniel Defoe, Henry Baker, 1703-1774), "On the Decomposition of Water," in explanation of some experiments, of which he had given an account at the British Association, 1846. In 1852 he was promoted to the rank of a Queen's Counsel, and made some interesting experiments on the passage of electricity through phosphoric vapours. In 1853 he published his work "On the Correlation of Forces," a masterly outline of the modern theory of Dynamics; and in 1856 it was translated into French by the Abbé Moigno. In 1858 he lectured in the Roya Institution, “On the Molecular Impressions by Light and Electricity;" and in 1859, in the same place, decisively announced the non-conduction of electricity in vacuo, and hence the necessity of matter to the transmissibility of electric currents. He is an acute observer, a clear reasoner, and an able experimenter. He is a 1866.

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practical expositor of science, and imparts a life-interest to his speculations. He is a notable man in many respects. He is a member of numerous scientific societies, a very frequent contributor to philosophical journals, transactions, &c. He has held the office of Vice-President in the Royal Institution and in the Royal Society. He is an enthusiastic supporter of the British Association, and has been elevated, most justly, to the premiership of this" Parliament of Science." At the meeting under his presidency held in Nottingham, 22nd of August, the speech from which the following rhetorical excerpts have been collected, and which contain the gist of the author's remarks as far as they are suited for popular exposition, was delivered with great effect. It cannot fail to add much to the author's already and deservedly great repute as a scientific thinker and an eloquent expositor of discovery in its relations to research.

After some introductory remarks, he addressed himself to the lessons already learned, and the probable prospects of improved natural knowledge. One word was the key to his discourse-continuity,— -no new word, and used in no new sense, but perhaps applied more generally than hitherto. He proposed to show that the development of observational, experimental, and even deductive knowledge, is either attained by steps so extremely small as to form a continuous ascent, or when distinct results, apparently separate from any co-ordinate phenomena, have been attained, that then, by the subsequent progress of science, intermediate links have been discovered, uniting the apparently segregated instances with other more familiar phenomena. In astronomy, from the time when the earth was considered a flat plain, bounded by a flat ocean,-when the sun, moon, and stars were regarded as lanterns to illuminate this plain,-each successive discovery has brought with it similitudes and analogies between this earth and many of the objects of the universe with which our senses, aided by instruments, have made us acquainted. The proofs that gravitation is not confined to our solar system, but pervades the universe, have received many confirmations by the labours of members of this association-Lord Rosse, Lord Wrottesley, and Sir J. Herschel, the two latter having devoted special attention to the orbits of double stars; the former to those probably more recent systems called nebulæ. Another class of quite recent observations has formed a special subject of contribution to the transactions of this association; I allude to those on meteorites, at which Professor Baden Powell assiduously laboured; and a series of star charts, for enabling observers of shooting stars to record their observations, laid before the association by Mr. Glaisher. Dr. Olmsted explains these to be cosmical bodies moving in the interplanetary space by gravitation round the sun, and some perhaps round planets. This view gives us a new element of continuity. The universe would thus appear not to have the extent of empty space formerly attributed to it, but to be studded between the larger and more visible masses with smaller planets, if the term be permitted to be applied to meteorites. The number of known asteroids, or bodies of a smaller size than what are termed the ancient planets, has been so increased by numerous discoveries, that instead of seven we now count eighty-eight as the number of recognized planets-a field of discovery with which the name of Hind will be ever associated. It is no farfetched speculation to suppose that between these asteroids and the meteorites bodies of intermediate size exist, until the space occupied by our solar system becomes filled up with planetary bodies, varying in size, from that of Jupiter (1,240 times larger in volume than the earth) to that

of a cannon ball, or even a pistol shot. The researches of Leverrier on the intraMercurial planets aid these views; and another half-century may, and not improbably will, enable us to ascertain that these seemingly vacant spaces are occupied by smaller bodies which have escaped observation, as the asteroids had until the time of Obers and Piazzi. But the evidence of continuity as pervading the universe does not stop at telescopic observation; chemistry and physical optics bring us new proofs. Those meteoric bodies come as travellers, bringing specimens of minerals from extra-terrestrial regions. M. Daubrée finds that the similarity of terrestrial rocks to meteorites increases as we penetrate the earth's crust, and that some of the deep-seated minerals have a composition and characteristics almost identical with meteorites. By experiments, he has succeeded in forming from terrestrial rocks substances very much resembling meteorites. Thus relationship is established between this earth and those wanderers from remote regions. While chemistry thus aids us in ascertaining the relationship of our planet to meteorites, its relation in composition to other planets, to the sun, and to more distant suns and systems, is aided by another science-viz., optics. That light passing from one transparent medium to another should carry with it evidence of the source from which it emanates, would, until lately, have seemed an extravagant supposition; but probably (could we read it) everything contains in itself a large portion of its own history.

The most remarkable achievement by spectrum analysis is the record of observations on a temporary star which shone forth this year in the constellation of the Northern Crown, about a degree S.E. of the stars. When first seen, May 12th, it

was nearly equal in brilliancy to a star of the second magnitude; when observed by Mr. Huggins and Dr. Miller, May 16th, it was reduced to the third or fourth magnitude. Examined by these observers with the spectroscope, it gave a spectrum which they state was unlike that of any celestial body they had examined. The light was compound, and had emanated from two different sources. One spectrum was analogous to that of the sun-viz., formed by the light of an incandescent solid or liquid photosphere, which had suffered absorption by the vapours of an envelope cooler than itself. The second spectrum consisted of a few bright lines, which indicated that the light by which it was formed was emitted by matter in the state of luminous gas. They consider that, from the position of two of the bright lines, the gas must be probably hydrogen, and from their brilliancy compared with the light of the photosphere, the gas must have been at a very high temperature. They imagine the phenomena to result from the burning of hydrogen with some other element, and that from the resulting temperature the photosphere is heated to incandescence. There is strong reason to believe that this star is one previously seen by Argelander and Sir J. Herschel, and that it is a variable star of long or irregular period; it is also notable that some of its spectrum lines cor respond with those of several variable stars. The time of its appearance was too short for any attempt to ascertain its parallax; it would have been important if it could even have been established that it is not a near neighbour, as the magnitude of such a phenomenon must depend upon its distance. It is a great triumph to have caught this fleeting object, and obtained permanent records for the use of future observers. While gravitation, physical constitution, and chemical analysis by the spectrum show us that matter has similar characteristics in other worlds than our own-when we pass to the consideration of those other attributes of matter which were at one time supposed to be peculiar kinds of matter itself, or, as they were called, imponderables, but which are now generally, if not universally, recognized as forces or modes of motion, we find the evidence of continuity still stronger. What are now magnetism and electricity? forces so universal, so apparently connected with matter, as to become two of its invariable attributes.

So with light, heat, and chemical affinity. Further than this, it seems to me that it is now proved that all these forces are so invariably connected inter se, and with motion, as to be regarded as modifications of each cther, and as resolving themselves objectively into motion, and subjectively into that something which produces or resists motion, and which we call force. One of the most startling suggestions as to force resulting from the dynamical theory of heat is by Mayer, that by the loss of vis viva occasioned by friction of the tidal waves, as well as by their forming, as it were, a drag upon the earth's rotatory movement, the velocity of the earth's rotation must be gradually diminishing, and that thus, unless some undiscovered compensatory action exist, this rotation must ultimately cease, and changes hardly calculable take place in the solar system. Another most interesting speculation of Mayer is that the heat of the sun is occasioned by friction or percussion of meteorites falling upon it. There are some difficulties, not perhaps insuperable, in this theory. Assuming the undulatory theory of light to be true, and that the motion which constitutes light is transmitted across the interplanetary spaces by a highly elastic ether, then, unless this motion is confined to one direction, unless there be no interference in the medium, and consequently no friction, light must lose something in its progress from distant luminous bodies -that is to say, must lose something as light; for the force is not lost, but its mode of action is changed. If light, then, is lost as light (and the observations of Struvé seem to show this to be so), what becomes of the transmitted force lost as light, but existing in some other form? So with heat our sun, our earth, and planets are constantly radiating heat into space, so in all probability are the other suns, the stars, and their attendant planets. What becomes of the heat thus radiated into space? If the universe have no limit,—and it is difficult to conceive one, there is a constant evolution of heat and light; and yet more is given off than is received by each cosmical body, for otherwise night would be as light and as warm as day. What becomes of the enormous force thus apparently non-recurrent in the same form? Does it return as palpable motion? Does it move or contribute to move suns and planets? and can it be conceived as a force similar to that which Newton speculated on as universally repulsive and capable of being substituted for universal attraction? We are in no position at present to answer such questions as these; but I know of no problem in celestial dynamics more deeply interesting than this, and we may be no further removed from its solution than the predecessors of Newton were from the simple dynamical relation of matter to matter which that potent intellect detected and demonstrated. Passing from extra-terrestrial theories to the narrower field of molecular physics, we find the doctrine of correlation of forces steadily making its way. In a practical point of view, the power of converting one mode of force into another is of the highest importance, and with reference to a subject which at present, somewhat prematurely perhaps, occupies men's minds-viz., the prospective exhaustion of our coal-fields, there is every encouragement derivable from the knowledge that we can at will produce heat by the expenditure of other forces; but, more than that, we may probably be enabled to absorb or store up, as it were, diffused energy; for instance, Berthelot has found that the potential energy of formate of potash is much greater than that of its proximate constituents, caustic potash and carbonic oxide. Carbonic oxide becomes, so to speak, reinvested with the amount of potential energy which its carbon possessed before uniting with oxygen, or, in other words, the carbonic oxide is raised as a force-possessor to the place of carbon by the direct absorption or conversion of heat from surrounding matter. Here we have, as to force-absorption, an analogous result to that of the formation of coal from carbonic acid and water. This and similar examples may calm apprehension as to means of supplying heat, should our present fuel become

exhausted. As the sun's force, spent in times long past, is now returned to us from the coal which was formed by that light and heat, so the sun's rays, which are daily wasted, so far as we are concerned, on the sandy deserts of Africa, may hereafter, by chemical or mechanical means, be made to light and warm the habitations of the denizens of colder regions. The tidal wave is, again, a large reservoir of force hitherto almost unused. The valuable researches of Professor Tyndall on radiant heat afford many instances of the power localizing, if the term be permitted, heat which would otherwise be dissipated. The discoveries of Graham, by which atmospheric air, drawn through films of caoutchouc, leaves behind half its nitrogen, or, in other words, becomes richer by half in oxygen, and hence has a nuch increased potential energy, not only show a most remarkable instance of physical molecular action merging into chemical, but afford us indications of means of storing up force,-much of the force used in working the aspirator being capable at any period, however remote, of being evolved by burning the oxygen with a combustible. What changes may take place in our modes of applying force before the coal-fields are exhausted it is impossible to predict. Even guesses at the probable period of their exhaustion are uncertain. It is true that we are at present far from seeing a practical mode of replacing that granary of force, the coal-fields; but we may with confidence rely on invention being in this case, as in others, born of necessity when the necessity arises. At a time when science and civilization cannot prevent large tracts of country being irrigated by human blood in order to gratify the ambition of a few restless men, it seems an over-refined sensibility to occupy ourselves with providing means for our descendants in the tenth generation to warm their dwellings or propel their locomotives. It is but a month from this time that the greatest triumph of force-conversion has been attained. The chemical action generated by a little salt water on a few pieces of zinc will now enable us to converse with the inhabitants of the opposite hemisphere of this planet, and—

"Put a girdle round about the earth in forty minutes."

The Atlantic Telegraph is an accomplished fact. In physiology very considerable strides are being made by studying the relation of organized bodies to external forces, and this branch of inquiry has been promoted by the labours of Carpenter, Bence Jones, Playfair, E. Smith, Frankland, and others. Vegetables acted on by light and heat decompose water, ammonia, and carbonic acid, and transform them into, among other substances, oxalate of lime, lactic acid, starch, sugar, stearine, urea, and ultimately albumen; while the animal reverses the process, as does vegetable decay, and produces from albumen, urea, stearine, sugar, starch, lactic acid, oxalate of lime, and ultimately ammonia, water, and carbonic acid. As, moreover, heat and light are absorbed or converted in forming the synthetic processes going on in the vegetable, so conversely heat and sometimes light is given off by the living animal; but it must not be forgotten that the line of demarcation between a vegetable and an animal is difficult to draw, that there are no single attributes which are peculiar to either, and that it is only by a number of characteristics that either can be defined. The ser es of processes above given may be simulated by the chemist in his laboratory; and the amount of labour which a man has undergone in the course of twenty-four hours may be approximately arrived at by an examination of the chemical changes which have taken place in his body; changed forms in matter indicating the anterior exercise of dynamical force. That muscular action is produced or supported by chemical change would probably now be a generally-accepted doctrine; but while many have thought that muscular power is derived from the oxidation of aibuminous or nitrogenized substances, several recent researches seem to show that the latter is rather