Thearle's "Theoretical Naval Architecture: a Treatise on the Angell's" Elements of Magnetism and Electricity." Temple's "Aids to Chemistry, specially designed for Students PAGE 421 422 422 422 423 Taylor's "The Aquarium, its Inhabitants, Structure, and Management." 423 SCIENTIFIC NOTES. Including Proceedings of Learned Societies at Home and Abroad, and Notices of Recent Scientific Literature. N selecting this subject we lay no claim either to the gift of second sight or to the possession of a clearer view of the future development of Science than may be the lot of our contemporaries. Nor is it our purpose to write an imitation of Winterl's celebrated "Prodromus," in which enthusiasts may find whatever they think proper. We seek merely to call the attention of our fellow-workers, and especially of students, to certain researches which hold out great promise, and which, if duly followed up, will undoubtedly have a most important influence on the very foundations of chemistry. It must be confessed that, as regards these very foundations, the alphabet of the science, our knowledge is not merely limited, but unsatisfactory in the highest degree. Look at our "elements." Most chemists quietly accept them as ultimate facts, and work with them-or perhaps play with them-more or less judiciously, quietly waiving all inquiry into their nature and their origin. Are they absolutely elementary bodies, distinct from the beginning, and resolvable neither into each other nor into any forms of matter still unknown? Or are they compounds, elementary in the mere relative acceptation that their decomposition is a task not within our present knowledge and power. Have we any evidence of their simplicity other than what our grandfathers had of the supposed elementary character of potash and soda prior to Davy's great discovery? If compounds, are they all of the same order, or are some of them, perhaps, resolvable into the remainder, whilst these, in turn, consist of ultimate—or at least ulterior-bodies, as yet undiscovered? If simple, are they like the wheels and pinions VOL. VII. (N.S.) U Some of a machine, or the parts of a dissected puzzle, definite in their number and purpose, and all necessary to a given result? Or are they a mere fragmentary and accidental group of objects with which we build our Lagerungs formel, just as children construct their sand forts and shell grottoes on the shore? What would be the impression of a man of inquiring mind if for the first time made acquainted with the so-called elements and their leading properties? He would see a list of some sixty bodies, from which, he is told, all things visible or tangible-all matter, in short-are compounded. But why their number should be between 60 and 70, rather than between 30 and 35 or between 160 and 170, no reason is given or even conjectured. Some of them, he is informed, such as oxygen, hydrogen, nitrogen, silicon, aluminium, and sulphur, are exceedingly abundant. Others, on the contrary,-as vanadium, thallium, indium, cæsium, and gallium, occur only in minute traces. are widely distributed, and others concentrated in comparatively few localities. Turning to their properties he finds equal difficulties. Here he will see a number of "elements" identical, or at least closely approaching, in their atomic weights. There, on the contrary, he finds wide gaps. Thus betweeen cerium (140) and erbium (178) there intervenes not an element. A smaller blank is found between bismuth (208) and thorium (231), between tungsten (184) and osmium (195), between zinc (65) and arsenic (75); whilst, on the contrary, between 86 and 96 we number six elements, and between 195 and 200 five (see Table I.). These gaps may, indeed, be possibly filled up by the discovery of some rare element, but there is also the possibility that new discoveries may fall in the more thickly-filled parts of the series. With those properties of the elements which cannot as yet be exhibited in a numerical series the case is very similar. There are groups showing a close approximation in their characters and behaviour. There are elements which stand comparatively isolated. How are all these facts to be explained on the theory of elements primordially distinct? Popular opinion, here as elsewhere, takes refuge in teleology. The elements in their respective proportions and in their distribution exist, as we find them, for the sake of man's convenience. We demur to this hypothesis. Look at sulphur; where existing in quantity the very key with which we unlock the treasurehouse of Nature-no less essential to the chemical technologist than is iron to the engineer; but where occurring in small quantities, what a source of evil! Take the case of coal there is probably no purpose to which we apply itin metallurgy, in the gas-manufacture, in the generation of steam, or in domestic economy-where its value is not seriously impaired, and where nuisance and danger are not occasioned by the presence of a small percentage of sulphur. Far too little and far too equally distributed to be worth, or even capable of, extraction, it is yet far too much to be inactive, or other than formidable. Or, again, take phosphorus: absolutely necessary to our existence, and, of course, most valuable when met with in quantities and forms capable of utilisation; but when found, as it so frequently is, in traces accompanying iron, it is the source of incalculable loss and annoyance. Or, consider arsenic : on teleological principles, surely, a substance so poisonous, and yet at the same time so useful for certain technological purposes, should have been concentrated in some few places. But we find it very widely disseminated, present to a serious extent in most iron pyrites, and thus contaminating sulphuric and hydrochloric acids, and through them a variety of other chemicals. On the other hand, we look at the case of gold had it been more abundant, its low affinity for oxygen and sulphur and its power of resisting the action of organic acids would have rendered it exceedingly important, both for manufacturing and domestic purposes. Were gold as plentiful as copper the latter metal would be entirely banished from dye- and print-works. As for the rarer metals, if they exert any function it escapes, as a rule, our notice, whilst not a few of them, if common, would have been highly important. Thus on teleological principles we see nothing to explain, either the number, the relative amount, or the local distribution of the elements of many of them, scarcely, even, the very existence. We turn, therefore, to another point of view. The array of the elements cannot fail to remind us of the general aspect of the organic world. It shows us the same gaps due to our old acquaintance, the "missing link," or rather to its non-appearance. In both cases we see certain groups well filled up, whilst other forms stand isolated. Both display species that are common and species that are rare. Hence it seems natural, in the one instance as in the other, to view existing forms not as originally present, but as the outcome of a process of evolution, or, if the reader likes the expression, the residue after a "struggle for existence." Certain forms not in harmony with the present general conditions have disappeared; certain others have maintained themselves, indeed, but only on a limited scale; whilst a third class are abundant because circumstances have been favourable to their formation and preservation. The analogy, it must be remembered, is not the closest, and must not be pushed too far. There is of necessity a wide difference between species composed of lifeless beings, incapable of growth, reproduction, and decay, and species consisting of living organisms. From the nature of the case there cannot occur in the "elements" any distinction corresponding to that between living and fossil organic forms. The "stone book" tells us nothing of extinct elements. Nor would we for a moment suggest that any of our present elements, however rare, is disappearing; that any new element is in the course of formation; or that the properties of such as exist are in course of modification. All such changes, in as far as they took place at all, must have been confined to the pre-geological epoch-to the time when our earth, or rather the matter of which it consists, was in a state very different from its present condition. Making, however, every allowance for these distinctions, if evolution is the law of the universe manifested in the heavenly bodies, in organic individuals, and in organic species, we shall probably recognise it also though under an especial aspect-in those elements from which stars and organisms are, in the last resort, compounded, But where is the evidence that the elements have been formed by the "expansion "* of some few antecedent principles, at present hidden, or perhaps from one only primordial kind of matter? Were our attention confined to our own planet we might perhaps find little either to verify or to confute our hypothesis. But if we institute a comparative examination of the chemical composition of different heavenly bodies, as revealed to us by the spectroscope, evidence will be found. Into its nature and value we will now proceed to enquire. On an examination of the spectrum of our sun we recognise certain elementary bodies as decidedly present in his atmosphere. These are sodium, calcium, barium, magnesium, iron, chrome, nickel, copper, zinc, hydrogen, aluminium, titanium, manganese, and possibly strontium, cadmium, and cobalt. The following terrestrial elements, however, appear to be absent :-Gold, silver, mercury, rubidium, tin, potassium, lead, antimony, arsenic, lithium, * See Quarterly Journal of Science, January, 1877, p. 26. |