Chapter I: Observations on the Mer De Glace 339 (11)

‘The flask thus half filled with water having a disk of ice swimming upon it was placed in a mixture of ice and water, being quite surrounded by the mixture. After an hour the disk within the flask was frozen to the glass. By shaking the flask the disk was liberated, but it froze again. This occurred as often as the shaking was repeated. The flask was permitted to remain for eight days in the mixture, which was preserved throughout at a temperature of 0° C. During this time a number of very regular and sharply defined ice-crystals were formed, and augmented very slowly in size. This is perhaps the best method of obtaining beautifully formed crystals of ice.

‘While, therefore, the outer ice which had to support the pressure of the atmosphere slowly melted, the water within the flask, whose freezing-point, on account of a defect of pressure, was 0°.0075 C. higher, deposited crystals of ice. The heat abstracted from the water in this operation had, moreover, to pass through the glass of the flask, which, together with the small difference of temperature, explains the slowness of the freezing process.’

A single additional condition in connection with this beautiful experiment I should like to have seen fulfilled--namely, that the water in which the flask was immersed, as well as that within it, should be purged of its air by boiling. It is just possible that the point of congelation may not be entirely independent of the presence of air in the water.

The revival of this subject by Professor Helmholtz has caused me to make a few additional experiments on the moulding and regelation of ice. The following illustrates both: A quantity of snowy powder was scraped from a block of clear ice and placed in a boxwood mould having a shape like the foot of a claret-glass. The ice-powder being squeezed by a hydraulic press, a clear mass of ice of the shape shown in section at the bottom of fig. 9 was the result. In another mould the same powder was squeezed so as to form small cylinders, three of which are shown separate in fig. 9. A third mould was then employed to form a cup of ice, which is shown at the top of fig. 9. Bringing all the parts into contact, they were cemented through regelation to form the claret-glass sketched in fig. 10, from which several draughts of wine might be taken, if the liquid were cooled sufficiently before pouring it into the cup of ice.

There are brass shapes used for the casting of flowers and other objects which answer admirably for experiments on the regelation of ice. One of them was purchased for me by Mr. Becker. Ice-powder squeezed into it regelated to a solid mass and came from the mould in the sharply defined form sketched in fig. 11.

* * * * *

I placed a small piece of ice in warm water and pressed it underneath the water by a second piece. The submerged morsel was so small that the vertical pressure was almost infinitesimal. It froze, notwithstanding, to the under surface of the superior piece of ice. Two pieces of ice were placed in a basin of warm water, and allowed to come together. They froze as soon as they touched each other. The parts surrounding the place of contact rapidly melted away, but the two pieces continued for a time united by a narrow bridge of ice. The bridge finally melted away, and the pieces were for a moment separated. But bodies which water wets, and against which it rises by capillary attraction, move spontaneously together upon water. The ice morsels did so, and immediately regelation again set in. A new bridge was formed, which in its turn was dissolved, and the pieces closed up as before. Thus a kind of pulsation was kept up by the two pieces of ice. They touched, froze, a bridge was formed and melted, leaving an interval between the pieces. Across this they moved, touched, froze, the same process being repeated over and over again.

We have here the explanation of the curious fact that when several large lumps of ice are placed in warm water and allowed to touch each other, regelation is maintained among them as long as they remain undissolved. The final fragments may not be the one-hundredth part of the original ones in size; but through the process just described, they incessantly lock themselves together until they finally disappear.

According to Professor James Thomson’s theory, to produce regelation the pieces of ice have to exercise pressure, in order to draw from the surrounding ice the heat necessary for the liquefaction of the compressed part; and then this water must escape and be refrozen. All this requires time. In the foregoing experiments, moreover, the water liquefied by the pressure issued into the surrounding warm water, but notwithstanding this the floating fragments regelated in a moment. It is not necessary that the touching surfaces should be flat; for in this case a film of water might be supposed to exist between them of the temperature 0° C. The surfaces in contact may be convex: they may be virtual _points_ that are about to touch each other, clasped all round by the warm liquid, which is rapidly dissolving them as they approach. Still they freeze immediately when they touch.

There are two points urged by Helmholtz--one in favour of the view he has adopted, and the other showing a difficulty associated with the view of Faraday--on which a few words may be said. ‘I found,’ says Helmholtz, ‘the strength and rapidity of the union of the pieces of ice in such complete correspondence with the amount of pressure employed, that I cannot doubt that the pressure is actually the sufficient cause of the union.’

But, according to Faraday’s explanation, the strength and quickness of the regelation must also go hand in hand with the magnitude of the pressure employed. Helmholtz rightly dwells upon the fact that the appressed surfaces are usually not perfectly congruent--that they really touch each other in a few points only, the pressure being, therefore, concentrated. Now the effect of pressure exerted on two pieces of ice at a temperature of 0° C. is not only to lessen the thickness of the liquid film between the pieces, but also to flatten out the appressed points, and thus to spread the film over a greater space. On both theories, therefore, the strength and quickness of the regelation ought to correspond to the magnitude of the pressure.

The difficulty referred to above is thus stated by Helmholtz: ‘In the explanation given by Faraday, according to which the regelation is caused by a contact action of ice and water, I find a theoretic difficulty. By the freezing of the water a very sensible quantity of heat would be set free; and it does not appear how this is to be disposed of.’

On the part of those who accept Faraday’s explanation, the answer here would be that the free heat is diffused through the adjacent ice. But against this it will doubtless be urged that ice already at a temperature of 0° C. cannot take up more heat without liquefaction. If this be true under all circumstances, Faraday’s explanation must undoubtedly be given up. But the essence of that explanation seems to be that the interior portions of a mass of ice require a higher temperature to dissolve them than that sufficient to cause fusion at the surface. When therefore two moist surfaces of ice at the temperature 0° are pressed together, and when, in virtue of the contact action assumed by Faraday, the film of water between them is frozen, the adjacent ice (which is now in the interior, and not at the surface as at first) is in a condition to withdraw by conduction, and without prejudice to its own solidity, the small amount of heat set free. Once granting the contact action claimed by Faraday, there seems to be no difficulty in disposing of the heat rendered sensible by the freezing of the film.

When the year is advanced, and after the ice imported into London has remained a long time in store, if closely examined, parcels of liquid water will be found in the interior of the mass. I enveloped ice containing such water-parcels in tinfoil, and placed it in a freezing mixture until the liquid parcels were perfectly congealed. Removing the ice from the freezing mixture, I placed it, covered by its envelope, in a dark room, and found, after a couple of hours’ exposure to a temperature somewhat over 0° C., the frozen parcels again liquid. _The heat which fused this interior ice passed through the firmer surrounding ice without the slightest visible prejudice to its solidity._ But if the freezing temperature of the ice-parcels be 0° C., then the freezing temperature of the mass surrounding them must be higher than 0° C., which is what the explanation of Faraday requires.

In a quotation at p. 389 I have attached to the description of a precaution taken by Professor Helmholtz the query ‘why?’ He states that water freed of its air sinks, without freezing, to a temperature far below 0° C.; while when a piece of ice is in the water it cannot so sink in temperature, but is invariably deposited in the solid form at 0° C. This surely proves ice to possess a special power of solidification over water. It is needless to say that the fact is general--that a crystal of any salt placed in a saturated solution of the salt always provokes crystallisation. Applying this fact to the minute film of water enclosed between two appressed surfaces of ice, it seems to me in the highest degree probable that the contact action of Faraday will set in, that the film will freeze and cement the pieces of ice together.[41]

[41] Both Professor Helmholtz and I have since agreed to consider the physical cause of regelation an open question.

Apart from the present discussion, the following observation is perhaps worth recording: It is well known that ice during a thaw disintegrates so as to form rude prisms whose axes are at right angles to the planes of freezing. I have often observed this action on a large scale during the winters that I spent as a student on the banks of the Lahn. The manner in which these prisms are in some cases formed is extremely interesting. On close inspection, a kind of cloudiness is observed in the interior of a mass of apparently perfect ice. Looked at through a strong lens, this cloudiness appears as striæ at right angles to the planes of freezing, and when the direction of vision is across these planes the ends of the striæ are apparent. The spaces between the striæ are composed of clear unclouded ice. When duly magnified, the objects which produce the striæ turn out to be piles of minute liquid flowers, whose planes are at right angles to the direction of the striæ.

* * * * *

Since writing the above, I have been favoured with a copy of a discourse delivered by Professor De la Rive, at the opening of the forty-ninth meeting of the Société Helvétique, which assembled in 1865 at Geneva. From this admirable _résumé_ of our present knowledge regarding glaciers I make the following extract, which, together with those from the lecture of Helmholtz, will show sufficiently how the subject is now regarded by scientific men: ‘Such, gentlemen,’ says M. De la Rive, ‘is a description of the phenomena of glaciers, and it now remains to explain them, to consult observation, and deduce from it the fundamental character of the phenomena. Observation teaches us that gravity is the motive force, and that this force acts upon a solid body--ice--imparting to it a slow and continuous motion. What are we to conclude from this? That ice is a solid which possesses the property of flowing like a viscous body--a conclusion which appears very simple, but which was nevertheless announced for the first time hardly five-and-twenty years ago by one of the most distinguished philosophers of Scotland, Professor James D. Forbes. This theory, for it truly is a theory, basing itself on facts as numerous as they are well observed, enunciates the principle that ice possesses the characteristic properties which belong to plastic bodies. Although he did not directly prove it, to Professor Forbes belongs not the less the great merit of insisting on the plasticity of ice, before Faraday, in discovering the phenomenon of regelation, enabled Tyndall to prove that the plasticity was real, at least partially.

‘The experiment of Faraday is classical in connexion with our subject. It consists, as you know, in this, that if two morsels of ice be brought into contact in water, which may be even warm, they freeze together. Tyndall immediately saw the application of Faraday’s experiment to the theory of glaciers; he comprehended that, since pieces of ice could thus solder themselves together, the substance might be broken, placed in a mould, compressed, and thus compelled to take the form of the cavity which contained it. A wooden mould, for example, embraces a spherical cavity; placing in it fragments of ice and squeezing them, we obtain an ice sphere; placing this sphere in a second mould with a lenticular cavity and pressing it, we transform the sphere into a lens. In this way we can impart any form whatever to ice.

‘Such is the discovery of Tyndall, which may well be thus named, particularly in view of its consequences. For all these moulds magnified become the borders of the valley in which a glacier flows. Here the action of the hydraulic press which has served for the experiments of the laboratory is replaced by the weight of the masses of snow and ice collected on the summits, and exerting their pressure on the ice which descends into the valley. Supposing, for example, between the spherical mould and the lenticular one, a graduated series of other moulds to exist, each of which differs very little from the one which precedes and from that which follows it, and that a mass of ice could be made to pass through all these moulds in succession, the phenomenon would then become continuous. Instead of rudely breaking, the ice would be compelled to change by insensible degrees from the spherical to the lenticular form. It would thus exhibit a plasticity which might be compared to that of soft wax. But ice is only plastic under _pressure_; it is not plastic under _tension_: and this is the important point which the vague theory of plasticity was unable to explain. While a viscous body, like bitumen or honey, may be drawn out in filaments by tension, ice, far from stretching in this way, breaks like glass under this action. These points well established by Tyndall, it became easy for him to explain the mechanism of glaciers, and by the aid of an English geometer, Mr. William Hopkins, to show how the direction of the crevasses of a glacier are the necessary consequences of its motion.’

* * * * *

I have quite recently had a mould constructed for me by Mr. Becker,[42] and yesterday (November 16, 1865) made with it an experiment which, on account of the ease with which it may be performed, will interest all those who care about exhibiting in a striking and instructive manner the effects of regelation. The mould is shown in fig. 12. It consists of two pieces of cast iron, A B C and D F G, slightly wedge-shaped and held together by the iron rectangle R E which is slipped over them. The inner face of A B C is shown in fig. 13. In it is hollowed out a semiring M N, with a semicylindrical passage O leading into it. The inner face of D F G is similarly hollowed out, so that when both faces are placed together, as in fig. 12, they enclose a ring 4 inches in external diameter, from M to N, and 3/4 of an inch in thickness, with the passage O, 1 inch in diameter, into which fits the polished iron plug P. At _q_ and _r_, fig. 13, are little pins which, fitting into holes corresponding to them, keep the slabs A B C and D F G from sliding over each other.

[42] I am continually indebted to this able mechanism for prompt and intelligent aid in the carrying out of my ideas.

The mould being first cooled by placing it for a short time in a mixture of ice and water, fragments of ice are stuffed into the orifice O and driven down with a hammer by means of the plug P. The bruised and broken ice separates at _x_, one portion going to the right, the other to the left. Driving the ice thus into the mould, piece after piece, it is finally filled. By removing the rectangle R E, the two halves of the mould are then separated, and a perfect ring of ice is found within. Two such rings soldered by regelation at _a_ are shown in fig. 14. It would be easy thus to construct a chain of ice. An hydraulic press may of course be employed in this experiment, but it is not necessary; with the hammer and plug beautiful rings of ice are easily obtained by the regelation of the crushed fragments.

I have now to add the description of an experiment which suggested itself to my ingenious friend Mr. Duppa, when he saw the ice-rings just referred to, and which was actually executed by him yesterday (the 16th) in the laboratory of the Royal Institution. Pouring a quantity of plaster of paris into a proper vessel, an ice-ring was laid upon the substance, an additional quantity of the cement being then poured over the ring. The plaster ‘set,’ enclosing the ring within it: the ring soon melted, leaving its perfect matrix behind. The mould was permitted to dry, and, molten lead being poured into the space previously occupied by the ice, a leaden ring was produced. Now ice can be moulded into any shape: statuettes, vases, flowers, and innumerable other ornaments can be formed from it. These enclosed in cement, in the manner suggested by Mr. Duppa, remain intact sufficiently long to enable the cement to set around them; they afterwards melt and disappear, leaving behind them perfect plaster moulds, from which casts can be taken.

V.

_CLOUDS._

From every natural fact invisible relations radiate, the apprehension of which imparts a measure of delight; and there is a store of pleasure of this kind ever at hand for those who have the capacity to turn natural appearances to account. It is pleasant, for example, to lie on one’s back upon a dry green slope and watch the clouds forming and disappearing in the blue heaven. A few days back the firmament was mottled with floating cumuli, from the fringes of which light of dazzling whiteness was reflected downwards, while the chief mass of the clouds lay in dark shadow. From the edge of one large cloud-field stretched small streamers, which, when attentively observed, were seen to disappear gradually, and finally to leave no trace upon the blue sky. On the opposite fringe of the same cloud, and beyond it, small patches of milky mist would appear, and curdle up, so as to form little cloudlets as dense apparently as the large mass beside which they were formed. The counter processes of production and consumption were evidently going on at opposite sides of the cloud. Even in the midst of the serene firmament, where a moment previously the space seemed absolutely void, white cloud-patches were formed, their sudden appearance exciting that kind of surprise which might be supposed to accompany the observation of a direct creative act.

These clouds were really the indicators of what was going on in the unseen air. Without them no motion was visible; but their appearance and disappearance proved not only the existence of motion, but also the want of homogeneity in the atmosphere. Though we did not see them, currents were mingling, possessing different temperatures and carrying different loads of invisible watery vapour. We know that clouds are not true vapour, but vapour precipitated by cold to water. We know also that the amount of water which the air can hold in the invisible state depends upon its temperature; the higher the temperature of the air, the more water will it be able to take up. But, when a portion of warm air, carrying its invisible charge, is invaded by a current of low temperature, the chilled vapour is precipitated, and a cloud is the consequence. In this way two parcels of moist air, each of which taken singly may be perfectly transparent, can produce by their mixture an opaque cloud. In the same way a body of clear humid air, when it strikes the cold summit of a mountain, may render that mountain ‘cloud-capped.’

An illustration of this process, which occurred some years ago in a Swedish ball-room, is recounted by Professor Dove. The weather was clear and cold, and the ball-room was clear and warm. A lady fainted, and air was thought necessary to her restoration. A military officer present tried to open the window, but it was frozen fast. He broke the window with his sword, the cold air entered, and _it snowed in the room_. A minute before this all was clear, the warm air sustaining a large amount of moisture in a transparent condition. When the colder air entered, the vapour was first condensed and then frozen. The admission of cool air even into our London ball-rooms produces mistiness. Mountain-chains are very effective in precipitating the vapour of our south-westerly winds; and this sometimes to such an extent as to produce totally different climates on the two sides of the same mountain-group. This is very strikingly illustrated by the observations of Dr. Lloyd on the rainfall of Ireland. Stations situated on the south-west side of a mountain-range showed a quantity of rain far in excess of that observed upon the north-east side. The winds in passing over the mountains were drained of their moisture, and were afterwards comparatively dry.

Two or three years ago I had an opportunity of witnessing a singular case of condensation at Mortain in Normandy. The tourist will perhaps remember a little chapel perched upon the highest summit in the neighbourhood. A friend and I chanced to be at this point near the hour of sunset. The air was cloudless, and the sun flooded the hillsides and valleys with golden light. We watched him as he gradually approached the crest of a hill, behind which he finally disappeared. Up to this point a sunny landscape of exquisite beauty was spread before us, the atmosphere being very transparent; but now the air seemed suddenly to curdle into mist. Five minutes after the sun had departed, a dense fog filled the valleys and drifted in fleecy masses up the sides of the hills. In an incredibly short time we found ourselves enveloped in local clouds so dense as to render our retreat a matter of some difficulty.

In this case, before the sun had disappeared the air was evidently nearly saturated with transparent vapour. But why did the vapour curdle up so suddenly when the sun departed? Was it because the withdrawal of his beams rendered the _air_ of the valleys colder, and thus caused the precipitation of the moisture diffused through the air? No. We must look for an explanation to a more direct action of the sun upon the atmospheric moisture. Let me explain. The beams which reach us from the sun are of a very composite character. A sheaf of white sunbeams is composed of an infinitude of coloured rays, the resultant effect of all upon the eye being the impression of whiteness. But though the colours, and shades of colour, which enter into the composition of a sunbeam are infinite, for the sake of convenience we divide them into seven, which are known as the prismatic colours.

The beams of the sun, however, produce _heat_ as well as light, and there are different _qualities_ of heat in the sunbeam as well as different qualities of light--nay, there are copious rays of heat in a sunbeam which give no light at all, some of which never even reach the retina at all, but are totally absorbed by the humours of the eye. Now, the same substance may permit rays of heat of a certain quality to pass freely through it, while it may effectually stop rays of heat of another quality. But in all cases the heat stopped is expended in heating the body which stops it. Now, water possesses this _selecting power_ in an eminent degree. It allows the blue rays of the solar beam to pass through it with facility, but it slightly intercepts the red rays, and absorbs with exceeding energy the _obscure rays_; and those are the precise rays which possess the most intense heating power.

We see here at once the powerful antagonism of the sun to the formation of visible fog, and we see, also, how the withdrawal of his beams may be followed by sudden condensation, even before the air has had any time to cool. As long as the solar beams swept through the valleys of Mortain, every particle of water that came in their way was reduced to transparent vapour by the heat which the particle itself absorbed; or, to speak more strictly, in the presence of this antagonism precipitation could not at all occur, and the atmosphere remained consequently clear.[43] But the moment the sun withdrew, the vapour followed, without opposition, its own tendency to condense, and its sudden curdling up was the consequence.

[43] At this time I was brooding over experiments on the absorption of radiant heat by aqueous vapour.

With regard to the _air_, its temperature may not only have remained sensibly unchanged for some time after the setting of the sun, but it may have actually become warmer through the heat set free by the act of condensation. It was not, therefore, the action of cold air upon the vapour which produced the effect, but it was the withdrawal of that solar energy which water has the power to absorb, and by absorbing to become dissipated in true vapour.

I once stood with a friend upon a mountain which commands a view of the glacier of the Rhone from its origin to its end. The day had been one of cloudless splendour, and there was something awful in the darkness of the firmament. This deepening of the blue is believed by those who know the mountains to be an indication of a humid atmosphere. The transparency, however, was wonderful. The summits of Mont Cervin and the Weisshorn stood out in clear definition, while the mighty mass of the Finsteraarhorn rose with perfect sharpness of outline close at hand. As long as the sun was high there was no trace of fog in the valleys, but as he sloped to the west the shadow of the Finsteraarhorn crept over the snow-fields at its base. A dim sea of fog began to form, which after a time rose to a considerable height, and then rolled down like a river along the flanks of the mountain. On entering the valley of the Rhone, it crossed a precipitous barrier, down which it poured like a cataract; but long before it reached the bottom it escaped from the shadow in which it had been engendered, and was hit once more by the direct beams of the sun. Its utter dissipation was the consequence, and though the billows of fog rolled on incessantly from behind, the cloud-river made no progress, but disappeared, as if by magic, where the sunbeams played upon it. The conditions were analogous to those which hold in the case of a glacier. Here the ice-river is incessantly nourished by the mountain snow: it moves down its valley, but does not advance in front. At a certain point the consumption by melting is equal to the supply, and here the glacier ceases. In the case before us the cloud-river, nourished by the incessant condensation of the atmospheric vapour, moved down its valley, but ceased at the point where the dissipating action of the sunbeams equalled the supply from the cloud-generator behind.

VI.

_KILLARNEY._

The total amount of heat which the sun sends annually to the earth is invariable, and hence if any portion of the earth’s surface during any given year be colder than ordinary, we may infer with certainty that some other portion of the surface is then warmer than ordinary. The port of Odessa owes its importance to a case of atmospheric compensation of this kind. Forty or fifty years ago, Western Europe received less than its normal amount of heat; the missing sunbeams fell upon the East, and Odessa became, to some extent, the granary from which the hungry West was fed. The position it then assumed it has since maintained. The atmosphere is the grand distributor of heat. It has its cold and warm currents--vast aërial rivers, which chill or cheer according to the proximate sources from which they are derived. In this present year 1860 the British Isles appear to lie near the common boundary of two such currents--the limit, however, shifting so as to cause both to pass over us in swift succession. Near this boundary line the atmospheric currents mingle, and the copious aqueous precipitation which we now observe is the result.

Superadded to this source of general rain, we have at Killarney local condensers in the neighbouring mountains. Round the cool crests of Carrantual and his peaked and craggy brothers the moist and tilted south-west wind curdles ceaselessly into clouds, which nourish the moss and heather whose decomposition produces the peat which clothes the disintegrated rocks. Grandly the vast cumuli build themselves in the atmosphere, hanging at times lazily over the mountains and mottling with their shadows the brown sides of the hills. Reddened by the evening sun, these clouds cast their hues upon the lakes, the crisped surface of which breaks up their images into broad spaces of diffused crimson light. On other days the cumuli seem whipped into dust, and scattered through the general air, mixing therewith as the smoke of London mingles with the supernatant atmosphere. Day by day the guides prophesy fine weather--the blackest cloud is ‘all for hate.’ You are assured that if you start to-day you will not get ‘a single dhrop’ of rain; you go, and are drenched; but the guide’s purpose is accomplished, the moderate sum of three and sixpence being added to his private store.

In ages past these mountain condensers acted differently. The wet winds of the ocean, which now descend in liquid showers upon the hills, once discharged their contents as snow. And a famous deposit they must have made. In addition to the charms which this region presents to every eye, the mind of him who can read the rocks aright is carried back to a time when deep snowbeds cumbered the mountain-slopes, and vast glaciers filled the vales. In neither England nor Wales do the traces of glacial action reach the magnitude which they exhibit here.

The Gap of Dunloe is the channel of an ancient glacier; and all through it the scratching and polishing may be traced. The flanks of the Purple Mountain have been planed down by the moving ice, and the rocky amphitheatre which the guides choose for the production of echoes has been scooped and polished by the same agency. Near the point where the road from the Gap joins that up the Black Valley is a slab of rock, which rivals the famous _Höllen Platte_ in Haslithal. The Black Valley, indeed, was the mould through which a great glacier from the adjacent mountains moved, ‘unhasting, unresting,’ grinding the rocks right and left, and filling the entire basin now occupied by the waters of the Upper Lake. All the islands of this lake are glacier domes. The shapes, moreover, which have suggested the fanciful names given to some of the rocks are entirely due to the planing of the ice. The ‘Cannon Rock,’ the ‘Giant’s Coffin,’ the ‘Man-of-War,’ and others, owe their forms to the mighty moulding-plane which in bygone ages passed over them.

I have spoken of the echoes in the Gap of Dunloe. They are very fine, and are usually awakened by a guide who plays a bugle, and to whom extra wages are paid on this account. The man times his operations so that the echo and the original sound shall not overlap, and he usually places his guests behind a hill-brow, which partially cuts away the direct sound, but offers no impediment to the echoes. He flourishes his trumpet, and pauses; the rocks respond, the first return of the sound being almost as strong as the blast itself; the sonorous pulses leap from crag to crag, and from them to the listener’s ear, diminishing in intensity and augmenting in softness the oftener they are reflected. Moore’s melody of ‘The Meeting of the Waters,’ suitably played, is thus returned with exquisite sweetness by the reflecting rocks.

The rain here is pitiless, but the march of the showering clouds over the mountains is sometimes very grand. One really good day is all that I have been able to number out of six spent on the banks of the Lower Lake, and even that day was ushered in by heavy rain. Afterwards, however, the cloud field broke, and the condensed vapours rolled themselves up into sphered masses, which sailed majestically through the ether. With some other visitors I rowed to the Upper Lake, landed at the base of the Purple Mountain, and with one companion climbed the latter to its crest. This is covered by loose masses of stone of a purplish hue, from which the mountain derives its name.

A few days previously I had been on the top of Mangerton, a spot selected by the guides as affording a prospect of the entire region of the Lakes. But Mangerton is a stupid mountain, and it is climbed by a wearisome pony track. It is incomparably inferior to the Purple Mountain. From the latter, on one side, we look into the heart of Magillicuddy’s Reeks, and shake hands with Carrantual across the Gap of Dunloe. It commands a splendid mountain panorama, and on the occasion of my visit showed the Reeks in their true character, as cloud-generators. A light wind swept across them. Far to westward, towards the sea, the air was cloudless; but over the Reeks its moisture was densely precipitated, and formed there a canopy which threw an inky gloom upon the mountains. The clouds sometimes descended so as to touch the summits, but for the most part they floated a little way above them, leaving the jagged outlines clear. From the Reeks the clouds were wafted westward; but here, meeting with warmer air, they diminished in size, the smaller ones melting quite away. Below us gleamed the Upper Lake, running in and out amid the mountains, fringed with woods and studded with islands covered with sunny foliage. From this lake a long, sinuous, and narrow outlet, called the Long Range, runs to the Middle Lake. The suddenness with which this lovely sheet of water opens on quitting the Long Range constitutes perhaps the greatest surprise which the traveller here encounters.

We walked along the ridge of the Purple Mountain ankle deep in elastic moss, with glorious views at either side. Arrived at the end of its greatest spur, the Middle and Lower Lakes with their islands, and the wooded and tortuous peninsula between them, lay before us. No view of the English lakes known to me could compete in loveliness with this one. We passed onward through the heather to the brow above the Bay of Glena, and there clambered down the mountain, helping ourselves by the trees which grasped with gnarled roots the mossed and slippy crags. At Glena we met our boat, and were rowed over the jerking waves to the island of Innisfallen, and thence to our hotel. Various bits of climbing were accomplished during my stay, and almost in every case in opposition to the guides. The Eagle Rock, for example, a truly noble mass, and others, were climbed, amid emphatic enunciations of ‘impossible.’ Yet these guides and boatmen are fine, hardy fellows, and of great endurance, but they appear averse to trying their strength under new conditions.

I write on a drenching day, and a strong wind which wails dismally round the house has roused the Lower Lake to foam and fury. Innisfallen looms feebly through the grey haze, but the opposite Toumies mountains are plunged in impenetrable gloom. All round the horizon is built a black cloud-wall, but the zenithal heaven is clear. Over the coping of this thunderous bulwark the sun shoots his rays, which, meeting the dropping cloud of the opposite heaven, paint upon it a complete and magnificent bow. Here the white beam enters the front of the falling drop, and is reflected at its back, emerging unravelled to its component hues. But the condition is, that after being thus unravelled, the coloured rays shall not diverge on quitting the drop. If they did, they would be lost immediately to the senses; but they are squeezed together to parallel sheaves, and thus their intensity is preserved through long aërial distances. Above the vivid bow hangs its spectral secondary brother, in which a double reflection within each raindrop enfeebles the colours, and inverts the order of succession.

Touched by the wand of law, the dross of facts becomes gold, the meanest being raised thereby to brotherhood with the highest. Thus the smoke of an Irish cabin lifts our speculations to the heavenly dome. We look through the cloudless air at the darkness of infinite space, and are met by the azure of the firmament--we look through a long reach of the same atmosphere at the bright sun or moon and see them orange or red. We look through the peat-smoke at a black rock, or at the dark branches of a yew, and see the smoke blue--we look through the same smoke at a cloud illuminated to whiteness by the sun and find the smoke red. The selfsame column of smoke may be projected against a bright and a dark portion of the same cloud, and thus made to appear blue and red at the same time. The blue belongs to the light _reflected_ from the smoke; the red to the light _transmitted_ through it. In like manner, the hues of the atmosphere are not due to colouring matter, but to the fact of its being a turbid medium. Through this we look at the blackness of unillumined space and see the blue; at the western heaven at sunset, and meet that light which steeps the clouds of evening in orange and crimson dyes.

VII.

_SNOWDON IN WINTER._

Tainted by the city air, and with gases not natural even to the atmosphere of London, I gladly chimed in with the proposal of an experienced friend to live four clear days at Christmas on Welsh mutton and mountain air. On the evening of the 26th of December 1860 Mr. Busk, Mr. Huxley, and I found ourselves at the Penryhn Arms Hotel in Bangor. Next morning we started betimes. The wind had howled angrily during the night. It now swept over the frozen road, carrying the looser snow along with it, shooting the crystals with projectile force against our faces, and compelling us to lean forward at a considerable angle to keep upon our feet. Our destination was Capel Curig, with a prospective design upon Snowdon; but we had no bâtons fit for the ascent. At Bethesda, however, after many vain enquiries in Welsh and English about walking-sticks, we found a shop which embraced among its multitudinous contents a sheaf of rake-handles. Two of these we purchased at fourpence each, and had them afterwards furnished with rings and iron spikes, at the total cost of one shilling. Thus provided, we hoped that ‘old Snowdon’s craggy chaos’ might be invaded with a hope of success.

On the morning of the 28th we issued from our hotel. A pale blue, dashed with ochre, and blending to a most delicate green, overspread a portion of the eastern sky. Grey cumuli, tinged ruddily here and there as they caught the morning light, swung aloft, but melted more and more as the day advanced. The eastern mountains were all thickly covered with newly fallen snow. The effect was unspeakably lovely. In front of us was Snowdon; over it and behind it the atmosphere was closely packed with dense brown haze, the lower filaments of which reached almost half-way down the mountain, but still left all its outline clearly visible through the attenuated fog. No ray of sunlight fell upon the hill, and the face which it turned towards us, too steep to hold the snow, exhibited a precipitous slope of rock, faintly tinted by the blue grey of its icy enamel. Below us was Llyn Mymbyr, a frozen plain; behind us the hills were flooded with sunlight, and here and there from the shaded slopes, which were illuminated chiefly by the light of the firmament, shimmered a most delicate blue.

This beautiful effect deserves a word of notice; many doubtless have observed it during the late snow. Ten days ago, in driving from Kirtlington to Glympton, the window of my cab became partially opaque by the condensation of the vapour of respiration. With the finger-ends little apertures were made in the coating, and when viewed through these the snow-covered landscape flashed incessantly with blue gleams. They rose from the shadows of objects along the road, which shadows were illuminated by the light of the sky. The blue light is best seen when the eye is in motion, thus causing the images of the shadows to pass over different parts of the retina. The whole shadow of a tree may thus be seen with stem and branches of the most delicate blue. I have seen similar effects upon the fresh _névés_ of the Alps, the shadow being that of the human body looked at through an aperture in a handkerchief thrown over the face. The same splendid effect was once exhibited in a manner never to be forgotten by those who witnessed it, on the sudden opening of a tent-door at sunrise on the summit of Mont Blanc.

At Pen-y-Gwrid Busk halted, purposing to descend to Llanberis by the road, while Huxley and I went forward to the small public-house known as Pen Pass. Here our guide, Robert Hughes, a powerful but elderly man, refreshed himself, and we quitted the road and proceeded for a short distance along a car-track which seemed to wind round a spur of Snowdon. ‘Is there no shorter way up?’ we demanded. ‘Yes; but I fear it is now impracticable,’ was the reply. ‘Go straight on,’ said Huxley, ‘and do not fear us.’

Up the man went with a spurt, suddenly putting on all his steam. The whisky of Pen Pass had given him a flash of energy, which we well knew could not last. In fact, the guide, though he acquitted himself admirably during the day, had at first no notion that we should reach the summit; and this made him careless of preserving himself at the outset. Toning him down a little, we went forward at a calmer pace. Crossing the spur, we came upon a pony-track on the opposite side. It was rendered conspicuous by the unbroken layer of snow which rested on it. Huxley took the lead, wading knee-deep for nearly an hour.

I, wishing to escape this labour, climbed the slopes to the right, and sought a way over the less loaded bosses of the mountain. On our remarking to Hughes that he had never assailed Snowdon under such conditions, he replied that he had, and under worse. The 12th of April last, he affirmed, was a worse day, and he had led a lady on that day almost to the summit. Unluckily for him, there was a smack of ‘bounce’ in the reply. It caused us to conclude that the same energy which had led the lady could lead us, and hence, when Huxley fell back, the guide was sent to the front, to break the way. He did this manfully for nearly an hour, at the end of which he seemed very jaded, and as he sat resting on a corner of rock I asked him whether he was tired. ‘I am,’ was his reply. Huxley gave him a sip of brandy, and I came for a short time to the front.

I had no gaiters, and my boots were incessantly filled with snow. My own heat sufficed for a time to melt the snow; but this clearly could not go on for ever. My left heel first became numbed and painful; and this increased till both feet were in great distress. I sought relief by quitting the track and trying to get along the impending shingle to the right. The high ridges afforded me some relief, but they were separated by couloirs in which the snow had accumulated, and through which I sometimes floundered waist-deep. The pain at length became unbearable; I sat down, took off my boots and emptied them; put them on again, tied Huxley’s pocket handkerchief round one ankle, and my own round the other, and went forward once more. It was a great improvement--the pain vanished, and did not return.

The scene was grand in the extreme. Before us were the buttresses of Snowdon, crowned by his conical peak; while below us were three llyns, black as ink, and contracting additional gloom from the shadow of the mountain. The lines of weathering had caused the frozen rime to deposit itself upon the rocks, as on the tendrils of a vine, the crags being fantastically wreathed with runners of ice. The summit, when we looked at it, damped our ardour a little; it seemed very distant, and the day was sinking fast. From the summit the mountain sloped downward to a col which linked it with a bold eminence to our right. At the col we aimed, and half an hour before reaching it we passed the steepest portion of the track. This I quitted, seeking to cut off the zig-zags, but gained nothing but trouble by the attempt. This difficulty conquered, the col was clearly within reach; on its curve we met a fine snow cornice, through which we broke at a plunge, and gained safe footing on the mountain-rim. The health and gladness of that moment were a full recompense for the entire journey into Wales.

We went upward along the edge of the cone with the noble sweep of the snow cornice at our left. The huts at the top were all cased in ice, and from their chimneys and projections the snow was drawn into a kind of plumage by the wind. The crystals had set themselves so as to present the exact appearance of feathers, and in some cases these were stuck against a common axis, so as accurately to resemble the plumes in soldiers’ caps. It was 3 o’clock when we gained the summit. Above and behind us the heavens were of the densest grey; towards the western horizon this was broken by belts of fiery red, which nearer the sun brightened to orange and yellow. The mountains of Flintshire were flooded with glory, and later on, through the gaps in the ranges, the sunlight was poured in coloured beams, which could be tracked through the air to the places on which their radiance fell. The scene would bear comparison with the splendours of the Alps themselves.

Next day we ascended the pass of Llanberis. The waterfalls, stiffened into pillars of blue ice, gave it a grandeur which it might not otherwise exhibit. The wind, moreover, was violent, and shook clouds of snow-dust from the mountain-heads. We descended from Pen-y-Gwrid to Beddgelert. What splendid skating surfaces the lakes presented--so smooth as scarcely to distort the images of the hills! A snow-storm caught us before we reached our hotel. This melted to rain during the night. Next day we engaged a carriage for Carnarvon, but had not proceeded more than two miles when we were stopped by the snow. Huge barriers of it were drifted across the road; and not until the impossibility of the thing was clearly demonstrated did we allow the postilion to back out of his engagement. Luckily our luggage was portable. Strapping our bags and knapsacks on our shoulders, partly through the fields, and partly along the less encumbered portions of the road, we reached Carnarvon on foot, and the evening of the 31st of December saw us safe in London.

VIII.

_VOYAGE TO ALGERIA TO OBSERVE THE ECLIPSE._

The opening of the Eclipse Expedition was not propitious. Portsmouth, on the 5th of December 1870, was swathed by a fog, which was intensified by smoke, and traversed by a drizzle of fine rain. At six P.M. I was on board the ‘Urgent.’ On Tuesday morning the weather was too thick to permit of the ship’s being swung and her compasses calibrated. The Admiral of the port, a man of very noble presence, came on board. Under his stimulus the energy which the weather had damped appeared to become more active, and soon after his departure we steamed down to Spithead. Here the fog had so far lightened as to enable the officers to swing the ship.

At three P.M. on Tuesday the 6th of December we got away, gliding successively past Whitecliff Bay, Bembridge, Sandown, Shanklin, Ventnor, and St. Catherine’s Lighthouse. On Wednesday morning we sighted the Isle of Ushant, on the French side of the Channel. The northern end of the island has been fretted by the waves into detached tower-like masses of rock of very remarkable appearance. In the Channel the sea was green, and opposite Ushant it was a brighter green. On Wednesday evening we committed ourselves to the Bay of Biscay. The roll of the Atlantic was full, but not violent. There had been scarcely a gleam of sunshine throughout the day, but the cloud-forms were fine, and their apparent solidity impressive. On Thursday morning I rose refreshed, and found the green of the sea displaced by a deep indigo blue. The whole of Thursday we steamed across the bay. We had little blue sky, but the clouds were again grand and varied--cirrus, stratus, cumulus, and nimbus, we had them all. Dusky hairlike trails were sometimes dropped from the distant clouds to the sea. These were falling showers, and they sometimes occupied the whole horizon, while we steamed across the rainless circle which was thus surrounded. Sometimes we plunged into the rain, and once or twice, by slightly changing course, avoided a heavy shower. From time to time perfect rainbows spanned the heavens from side to side. At times a bow would appear in fragments, showing the keystone of the arch midway in air, and its two buttresses on the horizon. In all cases the light of the bow could be quenched by a Nicol’s prism, with its long diagonal tangent to the arc. Sometimes gleaming patches of the firmament were seen amid the clouds. When viewed in the proper direction, the gleam could be quenched by a Nicol prism, a dark aperture being thus opened into stellar space.

At sunset on Thursday the denser clouds were fiercely fringed, while through the lighter ones seemed to issue the glow of a conflagration. On Friday morning we sighted Cape Finisterre, the extreme end of the arc which sweeps from Ushant round the Bay of Biscay. Calm spaces of blue, in which floated quietly scraps of cumuli, were behind us, but in front of us was a horizon of portentous darkness. It continued thus threatening throughout the day. Towards evening the wind strengthened to a gale, and at dinner it was difficult to preserve the plates and dishes from destruction. Our thinned company hinted that the rolling had other consequences. It was very wild when we went to bed. I slumbered and slept, but after some time was rendered actively conscious that my body had become a kind of projectile, which had the ship’s side for a target. I gripped the edge of my berth to save myself from being thrown out. Outside, I could hear somebody say that he had been thrown from his berth, and sent spinning to the other side of the saloon. The screw laboured violently amid the lurching; it incessantly quitted the water, and, twirling in the air, rattled against its bearings, and caused the ship to shudder from stem to stern. At times the waves struck us, not with the soft impact which might be expected from a liquid, but with the sudden solid shock of battering-rams. ‘No man knows the force of water,’ said one of the officers, ‘until he has experienced a storm at sea.’ These blows followed each other at quicker intervals, the screw rattling after each of them, until, finally, the delivery of a heavier stroke than ordinary seemed to reduce the saloon to chaos. Furniture crashed, glasses rang, and alarmed enquiries immediately followed. Amid the noises I heard one note of forced laughter; it sounded very ghastly. Men tramped through the saloon, and busy voices were heard aft, as if something there had gone wrong.