At Last: A Christmas in the West Indies

Over our heads bend the great arrow leaves and purple leafstalks of the Tanias; ¹³³ and mingled with them, leaves often larger still: oval, glossy, bright, ribbed, reflecting from their underside a silver light.  They belong to Arumas; ¹³⁴ and from their ribs are woven the Indian baskets and packs.  Above these, again, the Balisiers bend their long leaves, eight or ten feet long apiece; and under the shade of the leaves their gay flower-spikes, like double rows of orange and black birds’ beaks upside down.  Above them, and among them, rise stiff upright shrubs, with pairs of pointed leaves, a foot long some of them, pale green above, and yellow or fawn-coloured beneath.  You may see, by the three longitudinal nerves in each leaf, that they are Melastomas of different kinds—a sure token they that you are in the Tropics—a probable token that you are in Tropical America.

And over them, and among them, what a strange variety of foliage: look at the contrast between the Balisiers and that branch which has thrust itself among them, which you take for a dark copper-coloured fern, so finely divided are its glossy leaves.  It is really a Mimosa—Bois Mulâtre, ¹³⁵ as they call it here.  What a contrast again, the huge feathery fronds of the Cocorite palms which stretch right away hither over our heads, twenty and thirty feet in length.  And what is that spot of crimson flame hanging in the darkest spot of all from an under-bough of that low weeping tree?  A flower-head of the Rosa del Monte. ¹³⁶  And what is that bright straw-coloured fox’s brush above it, with a brown hood like that of an Arum, brush and hood nigh three feet long each?  Look—for you require to look more than once, sometimes more than twice—here, up the stem of that Cocorite, or as much of it as you can see in the thicket.  It is all jagged with the brown butts of its old fallen leaves; and among the butts perch broad-leaved ferns, and fleshy Orchids, and above them, just below the plume of mighty fronds, the yellow fox’s brush, which is its spathe of flower.

What next?  Above the Cocorites dangle, amid a dozen different kinds of leaves, festoons of a liane, or of two, for one has purple flowers, the other yellow—Bignonias, Bauhinias—what not?  And through them a Carat ¹³⁷ palm has thrust its thin bending stem, and spread out its flat head of fan-shaped leaves twenty feet long each: while over it, I verily believe, hangs eighty feet aloft the head of the very tree upon whose roots we are sitting.  For amid the green cloud you may see sprigs of leaf somewhat like that of a weeping willow; ¹³⁸ and there, probably, is the trunk to which they belong, or rather what will be a trunk at last.  At present it is like a number of round-edged boards of every size, set on end, and slowly coalescing at their edges.  There is a slit down the middle of the trunk, twenty or thirty feet long.  You may see the green light of the forest shining through it.  Yes.  That is probably the fig; or, if not, then something else.  For who am I, that I should know the hundredth part of the forms on which we look?—And above all you catch a glimpse of that crimson mass of Norantea which we admired just now; and, black as yew against the blue sky and white cloud, the plumes of one Palmiste, who has climbed toward the light, it may be for centuries, through the green cloud; and now, weary and yet triumphant, rests her dark head among the bright foliage of a Ceiba, and feeds unhindered on the sun.

There, take your tired eyes down again; and turn them right, or left, or where you will, to see the same scene, and yet never the same.  New forms, new combinations; a wealth of creative Genius—let us use the wise old word in its true sense—incomprehensible by the human intellect or the human eye, even as He is who makes it all, Whose garment, or rather Whose speech, it is.  The eye is not filled with seeing, or the ear with hearing; and never would be, did you roam these forests for a hundred years.  How many years would you need merely to examine and discriminate the different species?  And when you had done that, how many more to learn their action and reaction on each other?  How many more to learn their virtues, properties, uses?  How many more to answer the perhaps ever unanswerable question—How they exist and grow at all?  By what miracle they are compacted out of light, air, and water, each after its kind?  How, again, those kinds began to be, and what they were like at first?  Whether those crowded, struggling, competing shapes are stable or variable?  Whether or not they are varying still?  Whether even now, as we sit here, the great God may not be creating, slowly but surely, new forms of beauty round us?  Why not?  If He chose to do it, could He not do it?  And even had you answered that question, which would require whole centuries of observation as patient and accurate as that which Mr. Darwin employed on Orchids and climbing plants, how much nearer would you be to the deepest question of all—Do these things exist, or only appear?  Are they solid realities, or a mere phantasmagoria, orderly indeed, and law-ruled, but a phantasmagoria still; a picture-book by which God speaks to rational essences, created in His own likeness?  And even had you solved that old problem, and decided for Berkeley or against him, you would still have to learn from these forests a knowledge which enters into man, not through the head, but through the heart; which (let some modern philosophers say what they will) defies all analysis, and can be no more defined or explained by words than a mother’s love.  I mean, the causes and the effects of their beauty; that ‘Æsthetic of plants,’ of which Schleiden has spoken so well in that charming book of his, The Plant, which all should read who wish to know somewhat of ‘The Open Secret.’

But when they read it, let them read with open hearts.  For that same ‘Open Secret’ is, I suspect, one of those which God may hide from the wise and prudent, and yet reveal to babes.

At least, so it seemed to me, the first day that I went, awe struck, into the High Woods; and so it seemed to me, the last day that I came, even more awe-struck, out of them.

CHAPTER VIII: LA BREA

We were, of course, desirous to visit that famous Lake of Pitch, which our old nursery literature described as one of the ‘Wonders of the World.’  It is not that; it is merely a very odd, quaint, unexpected, and only half-explained phenomenon: but no wonder.  That epithet should be kept for such matters as the growth of a crystal, the formation of a cell, the germination of a seed, the coming true of a plant, whether from a fruit or from a cutting: in a word, for any and all those hourly and momentary miracles which were attributed of old to some Vis Formatrix of nature; and are now attributed to some other abstract formula, as they will be to some fresh one, and to a dozen more, before the century is out; because the more accurately and deeply they are investigated, the more inexplicable they will be found.

So it is; but the ‘public’ are not inclined to believe that so it is, and will not see, till their minds get somewhat of a truly scientific training.

If any average educated person were asked—Which seemed to him more wonderful, that a hen’s egg should always produce a chicken, or that it should now and then produce a sparrow or a duckling?—can it be doubted what answer he would give? or that it would be the wrong answer?  What answer, again, would he make to the question—Which is more wonderful, that dwarfs and giants (i.e. people under four feet six or over six feet six) should be exceedingly rare, or that the human race is not of all possible heights from three inches to thirty feet?  Can it be doubted that in this case, as in the last, the wrong answer would be given?  He would defend himself, probably, if he had a smattering of science, by saying that experience teaches us that Nature works by ‘invariable laws’; by which he would mean, usually unbroken customs; and that he has, therefore, a right to be astonished if they are broken.  But he would be wrong.  The just cause of astonishment is, that the laws are, on the whole, invariable; that the customs are so seldom broken; that sun and moon, plants and animals, grains of dust and vesicles of vapour, are not perpetually committing some vagary or other, and making as great fools of themselves as human beings are wont to do.  Happily for the existence of the universe, they do not.  But how, and still more why, things in general behave so respectably and loyally, is a wonder which is either utterly inexplicable, or explicable, I hold, only on the old theory that they obey Some One—whom we obey to a very limited extent indeed.  Not that this latter theory gets rid of the perpetual and omnipresent element of wondrousness.  If matter alone exists, it is a wonder and a mystery how it obeys itself.  If A Spirit exists, it is a wonder and a mystery how He makes matter obey Him.  All that the scientific man can do is, to confess the presence of mystery all day long; and to live in that wholesome and calm attitude of wonder which we call awe and reverence; that so he may be delivered from the unwholesome and passionate fits of wonder which we call astonishment, the child of ignorance and fear, and the parent of rashness and superstition.  So will he keep his mind in the attitude most fit for seizing new facts, whenever they are presented to him.  So he will be able, when he doubts of a new fact, to examine himself whether he doubts it on just grounds; whether his doubt may not proceed from mere self-conceit, because the fact does not suit his preconceived theories; whether it may not proceed from an even lower passion, which he shares (being human) with the most uneducated; namely, from dread of the two great bogies, Novelty and Size—novelty, which makes it hard to convince the country fellow that in the Tropics great flowers grow on tall trees, as they do here on herbs; size, which makes it hard to convince him that in far lands trees are often two and three hundred feet high, simply because he has never seen one here a hundred feet high.  It is not surprising, but saddening, to watch what power these two phantoms have over the minds of those who would be angry if they were supposed to be uneducated.  How often has one heard the existence of the sea-serpent declared impossible and absurd, on these very grounds, by people who thought they were arguing scientifically: the sea-serpent could not exist, firstly because—because it was so odd, strange, new, in a word, and unlike anything that they had ever seen or fancied; and, secondly, because it was so big.  The first argument would apply to a thousand new facts, which physical science is daily proving to be true; and the second, when the reputed size of the sea-serpent is compared with the known size of the ocean, rather more silly than the assertion that a ten-pound pike could not live in a half-acre pond, because it was too small to hold him.  The true arguments against the existence of a sea-serpent, namely, that no Ophidian could live long under water, and that therefore the sea-serpent, if he existed, would be seen continually at the surface; and again, that the appearance taken for a sea-serpent has been proved, again and again, to be merely a long line of rolling porpoises—these really sound arguments would be nothing to such people, or only be accepted as supplementing and corroborating their dislike to believe in anything new, or anything a little bigger than usual.

But so works the average, i.e. the uneducated and barbaric intellect, afraid of the New and the Big, whether in space or in time.  How the fear of those two phantoms has hindered our knowledge of this planet, the geologist knows only too well.

It was excusable, therefore, that this Pitch Lake should be counted among the wonders of the world; for it is, certainly, tolerably big.  It covers ninety-nine acres, and contains millions of tons of so-called pitch.

Its first discoverers, of course, were not bound to see that a pitch lake of ninety-nine acres was no more wonderful than any of the little pitch wells—‘spues’ or ‘galls,’ as we should call them in Hampshire—a yard across; or any one of the tiny veins and lumps of pitch which abound in the surrounding forests; and no less wonderful than if it had covered ninety-nine thousand acres instead of ninety-nine.  Moreover, it was a novelty.  People were not aware of the vast quantity of similar deposits which exist up and down the hotter regions of the globe.  And being new and big too, its genesis demanded, for the comfort of the barbaric intellect, a cataclysm, and a convulsion, and some sort of prodigious birth, which was till lately referred, like many another strange object, to volcanic action.  The explanation savoured somewhat of a ‘bull’; for what a volcano could do to pitch, save to burn it up into coke and gases, it is difficult to see.

It now turns out that the Pitch Lake, like most other things, owes its appearance on the surface to no convulsion or vagary at all, but to a most slow, orderly, and respectable process of nature, by which buried vegetable matter, which would have become peat, and finally brown coal, in a temperate climate, becomes, under the hot tropic soil, asphalt and oil, continually oozing up beneath the pressure of the strata above it.  Such, at least, is the opinion of Messrs. Wall and Sawkins, the geological surveyors of Trinidad, and of several chemists whom they quote; and I am bound to say, that all I saw at the lake and elsewhere, during two separate visits, can be easily explained on their hypothesis, and that no other possible cause suggests itself as yet.  The same cause, it may be, has produced the submarine spring of petroleum, off the shore near Point Rouge, where men can at times skim the floating oil off the surface of the sea; the petroleum and asphalt of the Windward Islands and of Cuba, especially the well-known Barbadoes tar; and the petroleum springs of the mainland, described by Humboldt, at Truxillo, in the Gulf of Cumana; and ‘the inexhaustible deposits of mineral pitch in the provinces of Merida and Coro, and, above all, in that of Maracaybo.  In the latter it is employed for caulking the ships which navigate the lake.’ ¹³⁹  But the reader shall hear what the famous lake is like, and judge for himself.  Why not?  He may not be ‘scientific,’ but, as Professor Huxley well says, what is scientific thought but common sense well regulated?

Running down, then, by steamer, some thirty-six miles south from Port of Spain, along a flat mangrove shore, broken only at one spot by the conical hill of San Fernando, we arrived off a peninsula, whose flat top is somewhat higher than the lowland right and left.  The uplands are rich with primeval forest, and perhaps always have been.  The lower land, right and left, was, I believe, cultivated for sugar, till the disastrous epoch of 1846: but it is now furred over with rastrajo woods.

We ran, on our first visit, past the pitch point of La Brea, south-westward to Trois, where an industrial farm for convicts had been established by my host the Governor.  We were lifted on shore through a tumbling surf; and welcomed by an intelligent and courteous German gentleman, who showed us all that was to be seen; and what we saw was satisfactory enough.  The estate was paying, though this was only its third year.  An average number of 77 convicts had already cleared 195 acres, of which 182 were under cultivation.  Part of this had just been reclaimed from pestilential swamp: a permanent benefit to the health of the island.  In spite of the exceptional drought of the year before, and the subsequent plague of caterpillars, 83,000 pounds of rice had been grown; and the success of the rice crop, it must be remembered, will become more and more important to the island, as the increase of Coolie labourers increases the demand for the grain.  More than half the plantains put in (22,000) were growing, and other vegetables in abundance.  But, above all, there were more than 7000 young coco-palms doing well, and promising a perpetual source of wealth for the future.  For as the trees grow, and the crops raised between them diminish, the coco-palms will require little or no care, but yield fruit the whole year round without further expense; and the establishment can then be removed elsewhere, to reclaim a fresh sheet of land.

Altogether, the place was a satisfactory specimen of what can be effected in a tropical country by a Government which will govern.  Since then, another source of profitable employment for West Indian convicts has been suggested to me.  Bamboo, it is now found, will supply an admirable material for paper; and I have been assured by paper-makers that those who will plant the West Indian wet lands with bamboo for their use, may realise enormous profits.

We scrambled back into the boat—had, of course, a heap of fruit, bananas, oranges, pine-apples, tossed in after us—and ran back again in the steamer to the famous La Brea.

As we neared the shore, we perceived that the beach was black as pitch; and the breeze being off the land, the asphalt smell (not unpleasant) came off to welcome us.  We rowed in, and saw in front of a little row of wooden houses a tall mulatto, in blue policeman’s dress, gesticulating and shouting to us.  He was the ward-policeman, and I found him (as I did all the coloured police) able and courteous, shrewd and trusty.  These police are excellent specimens of what can be made of the Negro, or half-Negro, if he be but first drilled, and then given a responsibility which calls out his self-respect.  He was warning our crew not to run aground on one or other of the pitch reefs, which here take the place of rocks.  A large one, a hundred yards off on the left, has been almost all dug away, and carried to New York or to Paris to make asphalt pavement.  The boat was run ashore, under his directions, on a spit of sand between the pitch; and when she ceased bumping up and down in the muddy surf, we scrambled out into a world exactly the hue of its inhabitants—of every shade, from jet-black to copper-brown.  The pebbles on the shore were pitch.  A tide-pool close by was enclosed in pitch: a four-eyes was swimming about in it, staring up at us; and when we hunted him, tried to escape, not by diving, but by jumping on shore on the pitch, and scrambling off between our legs.  While the policeman, after profoundest courtesies, was gone to get a mule cart to take us up to the lake, and planks to bridge its water-channels, we took a look round at this oddest of corners of the earth.

In front of us was the unit of civilisation—the police-station, wooden, on wooden stilts (as all well-built houses are here), to ensure a draught of air beneath them.  We were, of course, asked to come in and sit down, but preferred looking about, under our umbrellas; for the heat was intense.  The soil is half pitch, half brown earth, among which the pitch sweals in and out, as tallow sweals from a candle.  It is always in slow motion under the heat of the tropic sun: and no wonder if some of the cottages have sunk right and left in such a treacherous foundation.  A stone or brick house could not stand here: but wood and palm-thatch are both light and tough enough to be safe, let the ground give way as it will.

The soil, however, is very rich.  The pitch certainly does not injure vegetation, though plants will not grow actually in it.  The first plants which caught our eyes were pine-apples; for which La Brea is famous.  The heat of the soil, as well as of the air, brings them to special perfection.  They grow about anywhere, unprotected by hedge or fence; for the Negroes here seem honest enough, at least towards each other.  And at the corner of the house was a bush worth looking at, for we had heard of it for many a year.  It bore prickly, heart-shaped pods an inch long, filled with seeds coated with a red waxy pulp.

This was a famous plant—Bixa Orellana, Roucou; and that pulp was the well-known Arnotta dye of commerce.  In England and Holland it is used merely, I believe, to colour cheeses; but in the Spanish Main, to colour human beings.  The Indian of the Orinoco prefers paint to clothes; and when he has ‘roucoued’ himself from head to foot, considers himself in full dress, whether for war or dancing.  Doubtless he knows his own business best from long experience.  Indeed, as we stood broiling on the shore, we began somewhat to regret that European manners and customs prevented our adopting the Guaraon and Arawak fashion.

The mule-cart arrived; the lady of the party was put into it on a chair, and slowly bumped and rattled past the corner of Dundonald Street—so named after the old sea-hero, who was, in his lifetime, full of projects for utilising this same pitch—and up a pitch road, with a pitch gutter on each side.

The pitch in the road has been, most of it, laid down by hand, and is slowly working down the slight incline, leaving pools and ruts full of water, often invisible, because covered with a film of brown pitch-dust, and so letting in the unwary walker over his shoes.  The pitch in the gutter-bank is in its native place, and as it spues slowly out of the soil into the ditch in odd wreaths and lumps, we could watch, in little, the process which has produced the whole deposit—probably the whole lake itself.

A bullock-cart, laden with pitch, came jolting down past us; and we observed that the lumps, when the fracture is fresh, have all a drawn-out look; that the very air-bubbles in them, which are often very numerous, are all drawn out likewise, long and oval, like the air-bubbles in some ductile lavas.

On our left, as we went on, the bush was low, all of yellow Cassia and white Hibiscus, and tangled with lovely convolvulus-like creepers, Ipomœa and Echites, with white, purple, or yellow flowers.  On the right were negro huts and gardens, fewer and fewer as we went on—all rich with fruit-trees, especially with oranges, hung with fruit of every hue; and beneath them, of course, the pine-apples of La Brea.  Everywhere along the road grew, seemingly wild here, that pretty low tree, the Cashew, with rounded yellow-veined leaves and little green flowers, followed by a quaint pink and red-striped pear, from which hangs, at the larger and lower end, a kidney-shaped bean, which bold folk eat when roasted: but woe to those who try it when raw, for the acrid oil blisters the lips; and even while the beans are roasting, the fumes of the oil will blister the cook’s face if she holds it too near the fire.

As we went onward up the gentle slope (the rise is one hundred and thirty-eight feet in rather more than a mile), the ground became more and more full of pitch, and the vegetation poorer and more rushy, till it resembled, on the whole, that of an English fen.  An Ipomœa or two, and a scarlet-flowered dwarf Heliconia, kept up the tropic type, as does a stiff brittle fern about two feet high. ¹⁴⁰  We picked the weeds, which looked like English mint or basil, and found that most of them had three longitudinal nerves in each leaf, and were really Melastomas, though dwarfed into a far meaner habit than that of the noble forms we saw at Chaguanas, and again on the other side of the lake.  On the right, too, in a hollow, was a whole wood of Groo-groo palms, gray stemmed, gray leaved; and here and there a patch of white or black Roseau rose gracefully eight or ten feet high among the reeds.

The plateau of pitch now widened out, and the whole ground looked like an asphalt pavement, half overgrown with marsh-loving weeds, whose roots feed in the sloppy water which overlies the pitch.  But, as yet, there was no sign of the lake.  The incline, though gentle, shuts off the view of what is beyond.  This last lip of the lake has surely overflowed, and is overflowing still, though very slowly.  Its furrows all curve downward; and it is, in fact, as one of our party said, ‘a black glacier.’  The pitch, expanding under the burning sun of day, must needs expand most towards the line of least resistance, that is, downhill; and when it contracts again under the coolness of night, it contracts, surely from the same cause, more downhill than it does uphill; and so each particle never returns to the spot whence it started, but rather drags the particles above it downward toward itself.  At least, so it seemed to us.  Thus may be explained the common mistake which is noticed by Messrs. Wall and Sawkins ¹⁴¹ in their admirable description of the lake.

‘All previous descriptions refer the bituminous matter scattered over the La Brea district, and especially that between the village and the lake, to streams which have issued at some former epoch from the lake, and extended into the sea.  This supposition is totally incorrect, as solidification would have probably ensued before it had proceeded one-tenth of the distance; and such of the asphalt as has undoubtedly escaped from the lake has not advanced more than a few yards, and always presents the curved surfaces already described, and never appears as an extended sheet.’

Agreeing with this statement as a whole, I nevertheless cannot but think it probable that a great deal of the asphalt, whether it be in large masses or in scattered veins, may be moving very slowly downhill, from the lake to the sea, by the process of expansion by day, and contraction by night; and may be likened to a caterpillar, or rather caterpillars innumerable, progressing by expanding and contracting their rings, having strength enough to crawl downhill, but not strength enough to back uphill again.

At last we surmounted the last rise, and before us lay the famous lake—not at the bottom of a depression, as we expected, but at the top of a rise, whence the ground slopes away from it on two sides, and rises from it very slightly on the two others.  The black pool glared and glittered in the sun.  A group of islands, some twenty yards wide, were scattered about the middle of it.  Beyond it rose a noble forest of Moriche fan-palms; ¹⁴² and to the right of them high wood with giant Mombins and undergrowth of Cocorite—a paradise on the other side of the Stygian pool.

We walked, with some misgivings, on to the asphalt, and found it perfectly hard.  In a few yards we were stopped by a channel of clear water, with tiny fish and water-beetles in it; and, looking round, saw that the whole lake was intersected with channels, so unlike anything which can be seen elsewhere, that it is not easy to describe them.

Conceive a crowd of mushrooms, of all shapes, from ten to fifty feet across, close together side by side, their tops being kept at exactly the same level, their rounded rims squeezed tight against each other; then conceive water poured on them so as to fill the parting seams, and in the wet season, during which we visited it, to overflow the tops somewhat.  Thus would each mushroom represent, tolerably well, one of the innumerable flat asphalt bosses, which seem to have sprung up each from a separate centre, while the parting seams would be of much the same shape as those in the asphalt, broad and shallow atop, and rolling downward in a smooth curve, till they are at bottom mere cracks, from two to ten feet deep.  Whether these cracks actually close up below, and the two contiguous masses of pitch become one, cannot be seen.  As far as the eye goes down, they are two, though pressed close to each other.  Messrs. Wall and Sawkins explain the odd fact clearly and simply.  The oil, they say, which the asphalt contains when it rises first, evaporates in the sun, of course most on the outside of the heap, leaving a tough coat of asphalt, which has, generally, no power to unite with the corresponding coat of the next mass.  Meanwhile, Mr. Manross, an American gentleman, who has written a very clever and interesting account of the lake, ¹⁴³ seems to have been so far deceived by the curved and squeezed edges of these masses, that he attributes to each of them a revolving motion, and supposes that the material is continually passing from the centre to the edges, when it ‘rolls under,’ and rises again in the middle.  Certainly the strange stuff looks, at the first glance, as if it were behaving in this way; and certainly, also, his theory would explain the appearance of sticks and logs in the pitch.  But Messrs. Wall and Sawkins say that they observed no such motion; nor did we: and I agree with them, that it is not very obvious to what force, or what influence, it could be attributable.  We must, therefore, seek for some other way of accounting for the sticks—which utterly puzzled us, and which Mr. Manross well describes as ‘numerous pieces of wood which, being involved in the pitch, are constantly coming to the surface.  They are often several feet in length, and five or six inches in diameter.  On caching the surface they generally assume an upright position, one end being detained in the pitch, while the other is elevated by the lifting of the middle.  They may be seen at frequent intervals over the lake, standing up to the height of two or even three feet.  They look like stumps of trees protruding through the pitch; but their parvenu character is curiously betrayed by a ragged cap of pitch which invariably covers the top, and hangs down like hounds’ ears on either side.’

Whence do they come?  Have they been blown on to the lake, or left behind by man? or are they fossil trees, integral parts of the vegetable stratum below which is continually rolling upward? or are they of both kinds?  I do not know.  Only this is certain, as Messrs. Wall and Sawkins have pointed out, that not only ‘the purer varieties of asphalt, such as approach or are identical with asphalt glance, have been observed’ (though not, I think, in the lake itself) ‘in isolated masses, where there was little doubt of their proceeding from ligneous substances of larger dimensions, such as roots and pieces of trunks and branches;’ but moreover, that ‘it is also necessary to admit a species of conversion by contact; since pieces of wood included accidentally in the asphalt, for example, by dropping from overhanging vegetation, are often found partially transformed into the material.’  This is a statement which we verified again and again; as we did the one which follows, namely, that the hollow bubbles which abound on the surface of the pitch ‘generally contain traces of the lighter portions of vegetation,’ and ‘are manifestly derived from leaves, etc., which are blown about the lake by the wind, and are covered with asphalt, and as they become asphalt themselves, give off gases, which form bubbles round them.’