it; and a remark to be added is that some minds appear incapable of distinguishing between intrinsic absurdity and extrinsic absurdity. The case before us illustrates this remark; and at the same time shows us how analytical faculties of one kind may be constantly exercised without strengthening analytical faculties of another kind-how mathematical analysis may be daily practiced without any skill in psychological analysis being acquired. For, if these gentlemen had analyzed their own thoughts to any purpose, they would have known that incongruous juxtapositions may, by association of ideas, suggest characters that do not at all belong to the things juxtaposed. Did Mr. Kirkman ever observe the result of putting a bonnet on a nude statue? If he ever did, and if he then reasoned after the manner exemplified above, he doubtless concluded that the obscene effect belonged intrinsically to the statue, and only required the addition of the bonnet to make it conspicuous. The alternative conclusion, however, which perhaps most will draw, is that not in the statue itself was there anything of an obscene suggestion, but that this effect was purely adventitious: the bonnet, connected in daily experience with living women, calling up the thought of a living woman with the head dressed but otherwise naked. Similarly though, by clothing an idea in words which excite a feeling of the ludicrous by their oddity, any one may associate this feeling of the ludicrous with the idea itself, yet he does not thereby make the idea ludicrous; and, if he thinks he does, he shows that he has not practiced introspection to much purpose.

By way of a lesson in mental discipline, it may be not uninstructive here to note a curious kinship of opinion between these two mathematicians and two littérateurs. At first sight it appears strange that men, whose lives are passed in studies so absolutely scientific as those which Professor Tait and Mr. Kirkman pursue, should, in their judgments on the formula of evolution, be at one with two men of exclusively literary culture-a North American Reviewer and Mr. Matthew Arnold. In the "North American Review," vol. cxx., page 202, a critic, after quoting the formula of evolution, says, "This may be all true, but it seems at best rather the blank form for a universe than anything corresponding to the actual world about us." On which the comment may be, that one, who had studied celestial mechanics as much as the critic has studied the general course of transformations, might similarly have remarked that the formula, "bodies attract one another directly as their masses and inversely as the squares of their distances," was at best but a blank form for solar systems and sidereal clusters. With this parenthetical comment, I pass to the fact above hinted, that Mr. Matthew Arnold obviously coincides with the critic's estimate of the formula. In Chapter V. of his work "God and the Bible," when preparing the way for a criticism on German theologians as losing themselves in words, he quotes a saying from Homer. This he introduces by remarking that "it is not at all a grand one. We are almost

ashamed to quote it to readers who may have come fresh from the last number of the North American Review,' and from the great sentence there quoted as summing up Mr. Herbert Spencer's theory of evolution, 'Evolution is, etc.' Homer's poor little saying comes not in such formidable shape. It is only this: Wide is the range of words! words may make this way or that way." And then he proceeds with his reflections upon German logomachies. All of which makes it manifest that, going out of his way, as he does, to quote this formula from the "North American Review," he intends tacitly to indicate his agree ment in the reviewer's estimate of it.

That these two men of letters, like the two mathematicians, are unable to frame ideas answering to the words in which evolution at large is expressed, seems manifest. In all four, the verbal symbols used call up either no images, or images of the vaguest kinds, which, grouped together, form but the most shadowy thoughts. If, now, we ask what is the common trait in the education and pursuits of all four, we see it to be lack of familiarity with those complex processes of change which the concrete sciences bring before us. The men of letters, in their early days dieted on grammars and lexicons, and in their later days occupied with belles-lettres, biography, and a history made up mainly of personalities, are by their education and course of life. left almost without scientific ideas of a definite kind. The universality of physical causation, the interpretation of all things in terms of a never-ceasing redistribution of matter and motion, is naturally to them an idea utterly alien. The mathematician, too, and the mathematical physicist, occupied exclusively with the phenomena of number, space, and time, or, in dealing with forces, dealing with them in the abstract, carry on their researches in such ways as may, and often do, leave them quite unconscious of the traits exhibited by the general transformations which things, individually and in their totality, undergo. In a chapter on "Discipline," in the "Study of Sociology," I have commented upon the uses of the several groups of sciences-abstract, abstract-concrete, and concrete-in cultivating different powers of mind; and have argued that while, for complete preparation, the discipline of each group of sciences is indispensable, the discipline of any one group alone, or any two groups, leaves certain defects of judgment. Especially have I contrasted the analytical habit of thought which study of the abstract and abstract-concrete sciences produces with the synthetical habit of thought produced by study of the concrete sciences. And I have exemplified the defects of judgment to which the analytical habit, unqualified by the synthetical habit, leads. Here we meet with a striking illustration. Scientific culture of the analytical kind, almost as much as absence of scientific culture, leaves the mind. bare of those ideas with which the concrete sciences deal. Exclusive familiarity with the forms and factors of phenomena no more fits men for dealing with the products in their totalities than does mere literary study.

VOL. XVIL-45

IN

THE INDIA-RUBBER INDUSTRIES.*

BY THOMAS BOLAS, F. C. S.

NDIA-RUBBER, or caoutchouc, possesses properties so widely different from those of most other substances that it became an object of very great interest as soon as it made its appearance in the civilized world, and its industrial importance has rapidly increased as the knowledge of its remarkable characters and manifold applicability has become more extended. At the present time, caoutchouc holds such an important position with regard to the economy of modern arts and manufactures, that, were it suddenly to be withdrawn from circulation, many minor industries would in consequence cease to exist; while numerous large and important branches of handicraft would languish until arrangements could be made to adapt their operations to the altered circumstances.

It is, however, during the last forty years that India-rubber has enjoyed its greatest triumphs as an industrial agent-that is to say, since the art of vulcanization was discovered and perfected by the labors of Charles Goodyear, Thomas Hancock, and others.

The earliest rumor of the existence of caoutchouc reached Europe nearly five hundred years ago; the first visit of Columbus to Hayti having brought to light the fact that the natives of this island were in the habit of making playing-balls of an elastic gum. Nothing more appears to have been heard of India-rubber until Torquemada, rather over two hundred and fifty years ago, described the Mexican Indians as not only making playing-balls of India-rubber, but also as fabricating helmets, shoes, water-proof fabrics, and other articles of elastic gum. This writer gives some details as to the collection of the juice and the making of various articles from it, thus giving us the first view of the India-rubber manufacture as a branch of industry. We do not hear, hewever, of samples of India-rubber reaching Europe until long after this, and little more appears to have been learned regarding the substance until the celebrated French naturalist, La Condamine, made a communication to the Academy of Sciences at Paris concerning caoutchouc, he having had ample opportunities of studying the subject in Para. In the memoir in question, La Condamine gives very detailed particulars regarding the Para India-rubber tree, the collection and treatment of the juice, and the methods made use of by the natives for the production of various articles of caoutchouc. He tells us that the substance in question was used for making torches, these being only an inch and a half in diameter by two feet long, and yet burning for twelve hours. Again we hear of the use of India-rubber for the making of playing-balls, and it appears that the natives were in the habit of using enema or injection bottles made of caoutchouc.

* Lecture before the London Society of Arts.

Soon after La Condamine's communication to the Academy of Sciences, samples of India-rubber frequently reached Europe, and scientific men began to make investigations regarding this remarkable body. Between 1760 and 1770 we find Fresneau and Macquer studying the subject, and the last-named investigator made tubes and other articles of caoutchouc by dissolving it in ether and coating molds with the solution, so that a solid skin of caoutchouc should remain adherent to the mold on the evaporation of the solvent.

From this time until the end of the eighteenth century, the Indiarubber industry may be considered to have been undergoing its period of gestation, and to have been born with the dawn of the present century. Among the first of the important patents regarding the utilization of caoutchouc is that granted in 1823 to Charles Macintosh, for dissolving the substance in coal-oil, or coal-naphtha, and the use of this solution as a water-proofing agent. I have here a specimen of such a solution, as now manufactured by Messrs. Charles Macintosh and Co., of Manchester, together with some examples illustrating its

uses.

About the same time, elastic webbing was first made with threads cut from the raw rubber, and other minor applications of caoutchouc to the industrial arts were adopted from time to time, until the great discovery of vulcanization inaugurated a new epoch in this branch of industry, rendering it possible to so far alter caoutchouc as to make it capable of resisting, to a great extent, the action of heat on the one hand and cold on the other hand.

The milky sap of many plants contains caoutchouc, suspended in the form of minute transparent globules, these being frequently as small as too of an inch in diameter; but comparatively few plants contain sufficient caoutchouc to render them important sources of this body.

The trees which yield the largest supply of the best quality of caoutchouc consist of various species of hevea, which flourish in the northern districts of South America, especially in the province of Para, some portions of the valley of the Amazon being crowded to an extraordinary extent with heveas. The abundance of the India-rubber trees in Para may be judged of by the fact that this province alone exported 7,340 tons of caoutchouc in the year 1877, more than half of this being sent to Liverpool.

Among the heveas most productive of caoutchouc may be mentioned the Hevea Brasiliensis, which flourishes in Para, and yields some of the finest caoutchouc, and often attains a height of sixty to seventy feet, with a diameter of nearly three feet; the Hevea Guianensis, a similarly magnificent tree, likewise abundantly productive of caoutchouc; and the Hevea spruceana, a smaller tree, which grows almost exclusively in the province of Para. Fig. 1 represents the flowers and foliage of Hevea Guianensis.

In the operation of collecting the juice several cuts are made through the bark of the tree, and either shells or clay vessels are attached to receive the exuding milky sap. When sufficient of this has been collected, the operation of drying it is performed as follows: A kind of

wooden bat, thinly covered over with clay, is dipped into a pail filled with the juice, and the bat, thus coated, is held over a fire, fed with certain wild nuts, which, in burning, give off abundance of aromatic smoke. Fig. 2 represents this operation, and you will see that a kind