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est. Professor Jenkin's article on "The Atomic Theory of Lucretius" is both thorough and original; and in endeavouring to realize what Lucretius's theory of atoms was, and to understand how it en
stantiated by modern experimental science, | that they foreshadow the truth. Thereis to be found fully described only in Lu- fore the theory, as its old discoverers held cretius's poem. He has followed Epicu- it, has more than a mere historical interrus closely, as coincidences with the letters of Epicurus, preserved by Diogenes, make very plain. He has added perhaps nothing really new to the theory: his contribution to it is only a most eloquent and plain exposition of what he found in Epi-abled him to look upon nature and practicurus. One great aim of Lucretius's poem cally to grasp its force, the student is was to set forth the scientific truth of the greatly aided by it. We shall go over time, and its value in the eyes of science Lucretius's propositions one by one, giving, now lies in its full and exact statement of at the same time, their modern equivaan ancient theory, which the latest experi- lents, much as Professor Jenkin has done, ments confirm. This it is which at pres- also pointing out where we dissent from ent gives Lucretius so special an interest. him, particularly with regard to the moThe history of the atomic theory in tion of the atoms. Professor Clerk-Maxmodern times is well known. The name well's wonderful lecture on molecules, of the chemist in whose hands it acquired in which he describes the modern atom, a new force is now inseparably associated will also help us. Unscientific readers with it. Dalton assumed the existence of will remember at once with what a thrill atoms, conjectured that the weight of the of discovery they read it, and how they atoms making up each element is constant, seemed to themselves to follow a daring assigned different specific weights to the guide far into the region of the unknown. different kinds of atoms, discovered the The views of modern science with regard laws according to which they combine, to the process of evolution, the origination and thus founded his celebrated atomic of life, and the character of matter, as theory. So important were these discov-illustrated by Tyndall's presidential aderies and their results that Dalton has dress, will enable us to realize more defiearned the title of the "Father of Modern nitely, by comparison, what Lucretius's Chemistry." The progress of chemical actual creed on these points was. Both knowledge during the last century has Lucretius and Tyndall advocate evolution : been vitally connected with the hypothe-it is only to be expected that Tyndall's sis that there are such things as atoms, line of argument should be the more comultimate particles of matter, and its devel-plete of the two.
opments, nor is its value, as concerns Before beginning to set forth his philosfresh discovery, yet exhausted. In 1873 a well-known chemist, the president of the British Association, asked, in the course of his address, "What is the meaning of the great activity shown at present in chemistry." He answered the question thus: "Chemists are examining the combining properties of atoms, and get ting clearer views of the constitution of matter." Some of our readers may be surprised to find how similar the atom, as described by Lucretius, is to the modern chemical atom.
Professor Fleeming Jenkin, of Edinburgh, has gone over all Lucretius's statements in his first and second books as to the constitution of matter, and has shown that they are either certainly true, or else
ophy in due order, Lucretius expresses in the strongest way his obligations to his master: "When human life lay shamefully grovelling upon earth, crushed down under the weight of Religion, who showed her face from heaven, frowning upon mortals from on high with awful aspect, a man of Greece was the first who ventured to lift mortal eyes to her face, and the first to withstand her openly." Neither stories of the gods nor the thunders of heaven could make him afraid, but rather spurred him on, says the poet, to burst the bars of nature and find her secret. "Therefore the living force of his soul prevailed, and he passed out far beyond the flaming walls of the world,* and traversed in mind * What would Lucretius have said to the spectrum
the boundless universe, whence he returns, | understand, and therefore believe them to a conqueror, to tell us what can be and be done by divine power." But I will what cannot be; in short, on what princi- show, says Lucretius, how all things are ple each thing has its properties defined done "without the hand of the gods." Ferand its deep-set boundary-mark. Where- vently, and with submission, as Lucretius fore religion is put beneath our feet and realized the order of nature, the notion of trampled on in turn; us his victory raises deities interfering therewith must have to heaven." seemed to him mean indeed. This, his There is a boundless pity in the words first principle, holds true invariably of describing the misery of men owing to the matter once created, as we daily observe dominion of superstition- the same pity it, and is assumed in every scientific treaand enthusiasm for humanity that has made tise of to-day. By it Lucretius means to saints and philanthropists in all ages, from express that the laws of nature are conSaint Francis to Robert Owen (though, stant, that phenomena take place according perhaps, there was more of the latter in to well-defined laws, and that nothing the constitution of Lucretius). But we happens without a cause for it in nature. have quoted the passage to show what His illustrations of the principle show that, Epicurus was to Lucretius. Elsewhere he at any rate, he had distinctly grasped the designates him a god; the popular deities, fact of law as few, or perhaps none, in his he says, are small compared with him. It day can have done. This is the meaning is characteristic of the poet that, believing of his modern-sounding phrases about the in no God whose help could avail man-"law of nature." "It is absolutely dekind, he set up for worship the best thing creed," he says, "what each thing can do that he could find, a heroic man. But Lucretius is far more in earnest than he whom he delights to call his master. We cannot help questioning whether Epicurus would have approved of Lucretius's fervour even in the way of gratitude to himself. Was so great earnestness, even in the cause of his own philosophy, consistent with the calm and passionless tranquillity which the wise should seek? This passage, moreover, gives the keynote for the whole poem. It is science for the sake of theology that is here treated.
The first two books contain a number of propositions as to the qualities of the atoms, exactly what is denominated in our text-books the properties of matter.
The first proposition is that "nothing is ever begotten out of nothing by divine power." This outset is science and theology mingled, and it is, in this, characteristic of his whole work. "Men see many phenomena take place in earth and heaven, the causes of which they cannot
analysis, by which the chemist can literally pass beyond the "flaming walls of the world" (that is, the fiery
circuit of ether forming our heavens), and bring us tidings from the distant stars? Wonderful, indeed, he would have thought it; but he would have valued it most if it could have aided him in any way to prove that the gods have not created either the world or man, and are powerless whether for good or evil.
and what it cannot do, according to the
Our space will allow us only to name the next four propositions. The second, which completes the first, is that "nothing is ever annihilated, but all things on their dissolution go back into the first bodies,' that is, matter is imperishable. The third states the existence of void, but for which
See Tyndall's essay on "Prayer and Natural Law."
motion would be impossible. The next | nature," so small that it never has extwo are that all nature is made up of isted separate by itself, and will at no atoms and void, and that nothing else future time be able so to exist, since by but matter and void exists. its very nature it is a part of the other. We come now to the most interesting These parts appear to be quite identical part of Lucretius's system. The next with one another. Each part is a miniproposition conducts us to the atom.mum: nothing can be smaller than this "Some bodies," says the poet, "are first- and yet exist. These parts have existed beginnings of things, the remaining bodies from eternity side by side in the atom; are formed from a union of first-begin-"in a close-wedged mass they fill up the nings.' These first-beginnings of things composition of the first body." The are the Lucretian atoms. He also calls first-beginnings are not compounded from them "shapes," as they are conceived to the union of those parts, but are to be differ from each other in form, "first prin- considered strong in everlasting singleciples" (elementa), " matter as that from ness." Lucretius appears to have thought which things are made, "bodies" or three the smallest number of parts that an "seeds" of things. Anticipating a little, atom could have. Apparently he seems we may here try exactly to picture to our- to have conceived each "part" as represelves an atom as Lucretius conceives it. senting an angle or corner, so that an It is a little hard kernel, perfectly solid atom with three parts would appear to and indestructible. "The first-beginnings be a three-cornered or three-sided figure. of things no force can quench; they are As to shape, the atoms are not every sure to get the victory over it by their one of them "possessed of an equal solid body." Experience can give us no size and like shape with one another." notion of such solidity. Everything we They differ widely in form. Some are see around us in the world, however smaller. "The subtle fire of lightning is strong it may appear, -iron, stone, brass, formed of smaller shapes," and can pass - is yet destructible. Reason alone through openings better than "this our forces us to believe that the atoms are fire, which is born of wood and sprung not. Ordinary bodies have all void with- from pine." Light is formed of smaller in them; but first bodies are perfectly atoms than those of horn, and can theresolid. Without void "nothing can be fore pass through it. Some atoms have either crushed or broken up or cut in hooks by which they are fastened together, two" (nec findi in bina secundo, Lucretius, and come closer to each other. Hard who nowhere uses the word atom, by things, like diamond, basalt, iron, are these words exactly translates the Greek formed of such atoms. Slow-flowing oil Topo). Without void, a thing cannot ad- may have its atoms "larger or more mit within it the destroyers, wet or cold hooked and intertangled" than those of or fire. Therefore the atoms, being im- wine. In general, things which gratify penetrable and indivisible, are indestructi- the senses are formed of smooth and ble. Lucretius is fond of calling them round atoms; whatever is painful and "strong in their solid singleness.' This harsh, its elements are more hooked and is the most characteristic epithet which he rough. Again, "Some elements are with gives them. Each atom is a distinct, sep- justice thought to be neither smooth nor arate individual. Matter cannot be di- altogether hooked with curved points, but vided farther, after you have reduced it to rather to have very small angles slightly a collection of these individuals. Their projecting, so that they can rather tickle "singleness" (which means their distinct- than hurt the senses," for example, tartar ness of separate existence or individuality) of wine and elecampane. Apparently Luis their strength. Though they enter cretius supposes the different shapes of into infinite fresh combinations, "though the atoms to result altogether from the stricken by countless blows through eter- position in which the least parts are nity," they cannot be worn away. They placed within each. Every different arare as perfect and fresh to-day as when rangement of the parts yields a different the world was new. Each atom is per- manner of form of the atom." But there fectly hard, unchangeable and everlasting. is a limit to these differences: the num(Of the more accessory properties of mat- ber of shapes is finite, but the atoms of ter it is proved that Lucretius assumes each shape are infinite in number.† Epithem to be elastic.)
As to the composition of this little kernel, though extremely small, it yet has parts; each of these parts is "of a least
See the note on Book I., line 600, in Munro's "Lucretius," third edition, 1873.
In stating this, Lucretius supposes an atom formed of three least parts, and adds that "you may increase
It is interesting to know what was the reasoning by which Lucretius arrived at the result of ultimate atoms and their properties. He gives nine or ten arguments to prove either that there are atoms "of solid singleness," or that the atoms are indestructible: merely two forms of expressing the same statement. His reasoning is somewhat as follows:
curus held that the number of different has taken part in innumerable combinashapes, though not infinite, was inconceiv- tions, which have been formed and broken ably great. Lucretius merely proves that up and formed again, it remains fresh it must be finite. As to size, we must and perfect as ever. keep well in mind that the atom, as Lucretius conceived it, is a very tiny body. "The whole nature of the first-beginings," he says, "lies far beneath the ken of sense." Early in the first book he proves, by illustrations to which we shall afterwards refer, that "nature works by bodies which are invisible." This is why he so often uses the epithet "blind," that is, invisible, of the atoms and their move- In the first place, he holds that, admitments. But he insists emphatically that ting the existence of matter and void, the atoms are not infinitely small. Most each of these must of necessity exist "by likely Lucretius never thought of realiz-itself and unmixed." For, wherever void ing the size of his atom. Sir William is, there matter cannot be; and wherever Thomson says that if a drop of water body is, there void cannot be. That is to could be magnified to the size of our say, from the existence of void, absolutelv globe, the molecules composing it would empty space, Lucretius infers the exist appear to be of a size varying from that of ence of its opposite, the not-void, perfectshot to that of billiard-balls. Accordingly solid matter. Again, things, it is adto Clerk-Maxwell about two million mole- mitted, have all void within them; but cules of hydrogen placed in a row would how could they hold it in and continue to occupy .039 of an inch, and a million mil- keep it within them, unless their substance lion million million of them would weigh was perfectly solid, pure, unmixed matsomething more or less than seventy ter? Thirdly, having no void within grains troy. We question whether Lucretius would have assented to his atoms being rated at so small a size as this. In conclusion, Lucretius denies to the atoms all secondary qualities, which he sharply distinguishes from essential properties. They are colourless. They are not white or black or azure because existing things are white or black or azure. All colours can change into other colours, but that which changes is perishable, therefore the atoms are not endowed with colour. It is possible for us to conceive atoms colourless, just as "men who are born blind can yet recognize bodies by touch, though from the first they have never been associated in their minds with colour." Neither have they sound, or scent, or warmth, or cold. All such qualities belong to things which are perishable; but they must all be withdrawn from the first-beginnings, if we wish to assign for existing things imperishable foundations, for the safety of the universe to rest upon, that you may not have things returning altogether to nothing." Lastly, the atoms are void of sense-mere dead matter. Thus all their characteristics are here summed up. This, then, is the Lucretian atom, tiny yet so strong; after it
them by a few more." These words may be meant literally or not. It is calculated that from three parts six different shapes might be derived, from four twenty
four, from five 120, from six 720, from seven 5,040.
them, the atoms must be indestructible. (It is here — in its perfect solidity — that Lucretius's atom differs most from that of modern chemists, who, as Professor Clifford says, explain the hardness of solid matter "by the very rapid motion of something which is infinitely soft and yielding."
Lucretius has no notion of this.) He argues next that, admitting solid atoms, you can explain the existence of soft bodies, such as air, water, earth, by the admixture of void; but if your atoms are destructible and soft, how can the existence of hard bodies be explained? Moreover, Lucretius is persuaded that, as Professor Jenkin puts it, there is an immense "wear and tear going on" in nature; if the atoms were at all frail, "it is not consistent that they could have continued from eternity, though stricken and tossed about eternally by countless blows." To sustain these fearful shocks, the strain of eternal combinations from atoms to things, and dissolutions from things back to atoms — "under that strong pressure within the very jaws of death," Lucretius says there must be indestructible first-beginnings.
The sixth reason is an important one. We give it at more length, and in the poet's own words: "Had nature set no limit to the breaking of things, the bodies of matter would by this time have been reduced so far by the breaking of past
time, that nothing could be conceived out surely by a mere slip of the penof them and reach its full growth within "The hypothesis of the atoms is thus a fixed time." "But now, without a doubt, seen to be, in the first place, a mere a limit has been set to their breaking, and guess." We think that hardly any one, abides sure, since we see each thing pro- who has read attentively the above ab duced afresh, and, at the same time, well-stract of Lucretius's argument, will agree defined periods fixed for things, each after to the statement that his atomic theory is its kind, to reach the flower of their age." but "a guess." That is to say, we see in all the produc- This theory of Lucretius that there tions of nature that matter obeys definite really are such things as atoms, ultimate unchanging laws; therefore, in order to indivisible particles of matter, is now acproduce these regular results, the ultimate cepted. The modern chemist, too, bebasis of matter must be definite and un-lieves, like Lucretius, in a limited number changeable. Thus Lucretius deduces this property of the atoms from his great principle of law in nature, as illustrated by the regular periods within which growth and life go on. Lucretius justly feels the last to be a strong argument, and he repeats it in a slightly varied form : "Since nothing is changed, but all things are so constant that the different kinds of birds, all without intermission, exhibit on their body the distinctive marks of their species, they must, without doubt, also have their bodies formed of unchangeable matter. For if the first-beginnings of things could in any way be vanquished and changed, it would then be uncertain what could and what could not spring into being; in short, on what principle each thing has its properties fixed, and its deep-set boundary mark; nor could the generations so often reproduce, each after its kind, the nature, habits, way of life, and motions of the parents." Thus he again deduces the properties of the invisible atoms from the character of existing things which we can see, -for do not these represent the powers of the atoms? From the constancy of all the phenomena of nature (as illustrated by the distinctive marks, habits, and motions of various species), he infers that the atoms are unchangeable. Lastly, if nature allowed of division beyond the atom, if matter were infinitely divisible, then nothing could be reproduced out of such least parts, because particles which are infinitely small "cannot have the properties which birth-giving matter ought to have." Exactly to the same effect ClerkMaxwell says: "We do not assert that there is an absolute limit to the divisibility of matter what we assert is, that after we have divided a body into a certain finite number of constituent parts called molecules, then any further division of these molecules will deprive them of the properties which give rise to the phenomena observed in the substance."
Professor Seliar, in his admirable work on Lucretius, says, somewhat heedlessly
of different atoms, from each of which he
Therefore the song of nature over her task is,
No ray is gone, no atom worn,
My oldest force is good as new,
Gives back the bending heavens in dew.