Scott's Last Expedition/Volume 1/Chapter 7

From Wikisource
Jump to navigation Jump to search
Scott's Last Expedition, Volume I
by Robert Falcon Scott
Chapter VII
3963285Scott's Last Expedition, Volume I — Chapter VIIRobert Falcon Scott

CHAPTER VII

AT DISCOVERY HUT

Monday, March 6, a.m.—Roused the hands at 7.30. Wilson, Bowers, Garrard, and I went out to Castle Rock. We met Evans just short of his camp and found the loads had been dragged up the hill. Oates and Keohane had gone back to lead on the ponies. At the top of the ridge we harnessed men and ponies to the sledges and made rapid progress on a good surface towards the hut. The weather grew very thick towards the end of the march, with all signs of a blizzard. We unharnessed the ponies at the top of Ski slope—Wilson guided them down from rock patch to rock patch; the remainder of us got down a sledge and necessaries over the slope. It is a ticklish business to get the sledge along the ice foot, which is now all blue ice ending in a drop to the sea. One has to be certain that the party has good foothold. All reached the hut in safety. The ponies have admirably comfortable quarters under the verandah.

After some cocoa we fetched in the rest of the dogs from the Gap and another sledge from the hill. It had ceased to snow and the wind had gone down slightly. Page:Scott's Last Expedition, Volume 1.djvu/317 Turned in with much relief to have all hands and the animals safely housed.

Tuesday, March 7, a.m.—Yesterday went over to Pram Point with Wilson. We found that the corner of sea ice in Pram Point Bay had not gone out—it was crowded with seals. We killed a young one and carried a good deal of the meat and some of the blubber back with us.

Meanwhile the remainder of the party had made some progress towards making the hut more comfortable. In the afternoon we all set to in earnest and by supper time had wrought wonders.

We have made a large L-shaped inner apartment with packing cases, the intervals stopped with felt. An empty kerosene tin and some firebricks have been made into an excellent little stove, which has been connected to the old stove-pipe. The solider fare of our meals is either stewed or fried on this stove whilst the tea or cocoa is being prepared on a primus.

The temperature of the hut is low, of course, but in every other respect we are absolutely comfortable. There is an unlimited quantity of biscuit, and our discovery at Pram Point means an unlimited supply of seal meat. We have heaps of cocoa, coffee, and tea, and a sufficiency of sugar and salt. In addition a small store of luxuries, chocolate, raisins, lentils, oatmeal, sardines, and jams, which will serve to vary the fare. One way and another we shall manage to be very comfortable during our stay here, and already we can regard it as a temporary home.

Thursday, March 9, a.m.—Yesterday and to-day very busy about the hut and overcoming difficulties fast. The stove threatened to exhaust our store of firewood. We have redesigned it so that it takes only a few chips of wood to light it and then continues to give great heat with blubber alone. To-day there are to be further improvements to regulate the draught and increase the cooking range. We have further housed-in the living quarters with our old Discovery winter awning, and begin already to retain the heat which is generated inside. We are beginning to eat blubber and find biscuits fried in it to be delicious.

We really have everything necessary for our comfort and only need a little more experience to make the best of our resources. The weather has been wonderfully, perhaps ominously, fine during the last few days. The sea has frozen over and broken up several times already. The warm sun has given a grand opportunity to dry all gear.

Yesterday morning Bowers went with a party to pick up the stores rescued from the floe last week. E. Evans volunteered to join the party with Meares, Keohane, Atkinson, and Gran. They started from the hut about 10 a.m; we helped them up the hill, and at 7.30 I saw them reach the camp containing the gear, some 12 miles away. I don't expect them in till to-morrow night.

It is splendid to see the way in which everyone is learning the ropes, and the resource which is being shown. Wilson as usual leads in the making of useful suggestions and in generally providing for our wants. He is a tower of strength in checking the ill-usage of clothes—what I have come to regard as the greatest danger with Englishmen.

Friday, March 10, a.m.—Went yesterday to Castle Rock with Wilson to see what chance there might be of getting to Cape Evans.[1] The day was bright and it was quite warm walking in the sun. There is no doubt the route to Cape Evans lies over the worst corner of Erebus. From this distance the whole mountain side looks a mass of crevasses, but a route might be found at a level of 3,000 or 4,000 ft.

The hut is getting warmer and more comfortable. We have very excellent nights; it is cold only in the early morning. The outside temperatures range from 8° or so in the day to 2° at night. To-day there is a strong S.E. wind with drift. We are going to fetch more blubber for the stove.

Saturday, March 11, a.m.—Went yesterday morning to Pram Point to fetch in blubber—wind very strong to Gap but very little on Pram Point side.

In the evening went half-way to Castle Rock; strong bitter cold wind on summit. Could not see the sledge party, but after supper they arrived, having had very hard pulling. They had had no wind at all till they approached the hut. Their temperatures had fallen to −10° and −15°, but with bright clear sunshine in the daytime. They had thoroughly enjoyed their trip and the pulling on ski.

Life in the hut is much improved, but if things go too fast there will be all too little to think about and give occupation in the hut.

It is astonishing how the miscellaneous assortment of articles remaining in and about the hut have been put to useful purpose.

This deserves description.15

Monday, March 13, a.m.—The weather grew bad on Saturday night and we had a mild blizzard yesterday. The wind went to the south and increased in force last night, and this morning there was quite a heavy sea breaking over the ice foot. The spray came almost up to the dogs. It reminds us of the gale in which we drove ashore in the Discovery. We have had some trouble with our blubber stove and got the hut very full of smoke on Saturday night. As a result we are all as black as sweeps and our various garments are covered with oily soot. We look a fearful gang of ruffians. The blizzard has delayed our plans and everyone's attention is bent on the stove, the cooking, and the various internal arrangements. Nothing is done without a great amount of advice received from all quarters, and consequently things are pretty well done. The hut has a pungent odour of blubber and blubber smoke. We have grown accustomed to it, but imagine that ourselves and our clothes will be given a wide berth when we return to Cape Evans.

Wednesday, March 15, a.m.—It was blowing continuously from the south throughout Sunday, Monday, and Tuesday—I never remember such a persistent southerly wind.

Both Monday and Tuesday I went up Crater Hill. I feared that our floe at Pram Point would go, but yesterday it still remained, though the cracks are getting more open. We should be in a hole if it went.[2]

As I came down the hill yesterday I saw a strange figure advancing and found it belonged to Griffith Taylor. He and his party had returned safely. They were very full of their adventures. The main part of their work seems to be rediscovery of many facts which were noted but perhaps passed over too lightly in the Discovery—but it is certain that the lessons taught by the physiographical and ice features will now be thoroughly explained. A very interesting fact lies in the continuous bright sunshiny weather which the party enjoyed during the first four weeks of their work. They seem to have avoided all our stormy winds and blizzards.

But I must leave Griffith Taylor to tell his own story, which will certainly be a lengthy one. The party gives Evans [P.O.] a very high character.

To-day we have a large seal-killing party. I hope to get in a good fortnight's allowance of blubber as well as meat, and pray that our floe will remain.

Friday, March 17, a.m.—We killed eleven seals at Pram Point on Wednesday, had lunch on the Point, and carried some half-ton of the blubber and meat back to camp—it was a stiff pull up the hill.

Yesterday the last Corner Party started: E. Evans, Wright, Crean, and Forde in one team; Bowers, Oates, Cherry-Garrard, and Atkinson in the other. It was very sporting of Wright to join in after only a day's rest. He is evidently a splendid puller.

Page:Scott's Last Expedition, Volume 1.djvu/324 Page:Scott's Last Expedition, Volume 1.djvu/325 Page:Scott's Last Expedition, Volume 1.djvu/326 Page:Scott's Last Expedition, Volume 1.djvu/328 As I write the wind is blowing up again and looks like returning to the south. The only comfort is that these strong cold winds with no sun must go far to cool the waters of the Sound.

The continuous bad weather is trying to the spirits, but we are fairly comfortable in the hut and only suffer from lack of exercise to work off the heavy meals our appetites demand.

Tuesday, March 21.—The wind returned to the south at 8 last night. It gradually increased in force until 2 a.m., when it was blowing from the S.S.W., force 9 to 10. The sea was breaking constantly and heavily on the ice foot. The spray carried right over the Point—covering all things and raining on the roof of the hut. Poor Vince's cross, some 30 feet above the water, was enveloped in it.

Of course the dogs had a very poor time, and we went and released two or three, getting covered in spray during the operation—our wind clothes very wet.

This is the third gale from the south since our arrival here. Any one of these would have rendered the Bay impossible for a ship, and therefore it is extraordinary that we should have entirely escaped such a blow when the Discovery was in it in 1902.

The effects of this gale are evident and show that it is a most unusual occurrence. The rippled snow surface of the ice foot is furrowed in all directions and covered with briny deposit—a condition we have never seen before. The ice foot at the S.W. corner of the bay is broken down, bare rock appearing for the first time.

The sledges, magnetic huts, and in fact every exposed object on the Point are thickly covered with brine. Our seal floe has gone, so it is good-bye to seals on this side for some time.

The dogs are the main sufferers by this continuance of phenomenally terrible weather. At least four are in a bad state; some six or seven others are by no means fit and well, but oddly enough some ten or a dozen animals are as fit as they can be. Whether constitutionally harder or whether better fitted by nature or chance to protect themselves it is impossible to say—Osman, Czigane, Krisravitsa, Hohol, and some others are in first-rate condition, whilst Lappa is better than he has ever been before.

It is so impossible to keep the dogs comfortable in the traces and so laborious to be continually attempting it, that we have decided to let the majority run loose. It will be wonderful if we can avoid one or two murders, but on the other hand probably more would die if we kept them in leash.

We shall try and keep the quarrelsome dogs chained up.

The main trouble that seems to come on the poor wretches is the icing up of their hindquarters; once the ice gets thoroughly into the coat the hind legs get half paralysed with cold. The hope is that the animals will free themselves of this by running about.

Well, well, fortune is not being very kind to us. This month will have sad memories. Still I suppose things might be worse; the ponies are well housed and are doing exceedingly well, though we have slightly increased their food allowance.

Yesterday afternoon we climbed Observation Hill to see some examples of spheroidal weathering—Wilson knew of them and guided. The geologists state that they indicate a columnar structure, the tops of the columns being weathered out.

The specimens we saw were very perfect. Had some interesting instruction in geology in the evening. I should not regret a stay here with our two geologists if only the weather would allow us to get about.

This morning the wind moderated and went to the S.E.; the sea naturally fell quickly. The temperature this morning was +17°; minimum +11°. But now the wind is increasing from the S.E. and it is momentarily getting colder.

Thursday, March 23, a.m.—No signs of depôt party, which to-night will have been a week absent. On Tuesday afternoon we went up to the Big Boulder above Ski slope. The geologists were interested, and we others learnt something of olivines, green in crystal form or oxidized to bright red, granites or granulites or quartzites, hornblende and felspars, ferrous and ferric oxides of lava acid, basic, plutonic, igneous, eruptive—schists, basalts, &c. All such things I must get clearer in my mind.[3]

Tuesday afternoon a cold S.E. wind commenced and blew all night.

Yesterday morning it was calm and I went up Crater Hill. The sea of stratus cloud hung curtain-like over the Strait—blue sky east and south of it and the Western Mountains bathed in sunshine, sharp, clear, distinct—a glorious glimpse of grandeur on which the curtain gradually descended. In the morning it looked as though great pieces of Barrier were drifting out. From the hill one found these to be but small fragments which the late gale had dislodged, leaving in places a blue wall very easily distinguished from the general white of the older fractures. The old floe and a good extent of new ice had remained fast in Pram Point Bay. Great numbers of seals up as usual. The temperature was up to +20° at noon. In the afternoon a very chill wind from the east, temperature rapidly dropping till zero in the evening. The Strait obstinately refuses to freeze.

We are scoring another success in the manufacture of blubber lamps, which relieves anxiety as to lighting as the hours of darkness increase.

The young ice in Pram Point Bay is already being pressed up.

Friday, March 24, a.m.—Skuas still about, a few—very shy—very dark in colour after moulting.

Went along Arrival Heights yesterday with very keen over-ridge wind—it was difficult to get shelter. In the evening it fell calm and has remained all night with temperature up to +18°. This morning it is snowing with fairly large flakes.

Yesterday for the first time saw the ice foot on the south side of the bay, a wall some 5 or 6 feet above water and 12 or 14 feet below; the sea bottom quite clear with the white wall resting on it. This must be typical of the ice foot all along the coast, and the wasting of caves at sea level alone gives the idea of an overhanging mass. Very curious and interesting erosion of surface of the ice foot by waves during recent gale.

The depôt party returned yesterday morning. They had thick weather on the outward march and missed the track, finally doing 30 miles between Safety Camp and Corner Camp. They had a hard blow up to force 8 on the night of our gale. Started N.W. and strongest S.S.E.

The sea wants to freeze—a thin coating of ice formed directly the wind dropped; but the high temperature does not tend to thicken it rapidly and the tide makes many an open lead. We have been counting our resources and arranging for another twenty days' stay.

Saturday, March 25, a.m.—We have had two days of surprisingly warm weather, the sky overcast, snow falling, wind only in light airs. Last night the sky was clearing, with a southerly wind, and this morning the sea was open all about us. It is disappointing to find the ice so reluctant to hold; at the same time one supposes that the cooling of the water is proceeding and therefore that each day makes it easier for the ice to form—the sun seems to have lost all power, but I imagine its rays still tend to warm the surface water about the noon hours. It is only a week now to the date which I thought would see us all at Cape Evans.

The warmth of the air has produced a comparatively uncomfortable state of affairs in the hut. The ice on the Page:Scott's Last Expedition, Volume 1.djvu/334 say majority of people seem anxious to get exercise, but one or two like the fire better.

The dogs are getting fitter each day, and all save one or two have excellent coats. I was very pleased to find one or two of the animals voluntarily accompanying us on our walk. It is good to see them trotting against a strong drift.

Tuesday, March 28.—Slowly but surely the sea is freezing over. The ice holds and thickens south of Hut Point in spite of strong easterly wind and in spite of isolated water holes which obstinately remain open. It is difficult to account for these—one wonders if the air currents shoot downward on such places; but even so it is strange that they do not gradually diminish in extent. A great deal of ice seems to have remained in and about the northern islets, but it is too far to be sure that there is a continuous sheet.

We are building stabling to accommodate four more ponies under the eastern verandah. When this is complete we shall be able to shelter seven animals, and this should be enough for winter and spring operations.

Thursday, March 30.—The ice holds south of Hut Point, though not thickening rapidly—yesterday was calm and the same ice conditions seemed to obtain on both sides of the Glacier Tongue. It looks as though the last part of the road to become safe will be the stretch from Hut Point to Turtle-back Island. Here the sea seems disinclined to freeze even in calm weather. To-day there is more strong wind from the east. White horse all along under the ridge.

Page:Scott's Last Expedition, Volume 1.djvu/336 Page:Scott's Last Expedition, Volume 1.djvu/337 Bay—several off Pram Point in the shelter of Horse Shoe Bay. A great many fish in sea ice—mostly small, but a second species 5 or 6 inches long: imagine they are chased by seals and caught in brashy ice where they are unable to escape. Came back over hill: glorious sunset, brilliant crimson clouds in west.

Returned to find wind dropping, the first time for three days. It turned to north in the evening. Splendid aurora in the night; a bright band of light from S.S.W. to E.N.E. passing within 10° of the zenith with two waving spirals at the summit. This morning sea to north covered with ice. Min. temp, for night −5°, but I think most of the ice was brought in by the wind. Things look more hopeful. Ice now continuous to Cape Evans, but very thin as far as Glacier Tongue; three or four days of calm or light winds should make everything firm.

Wednesday, April 5, a.m.—The east wind has continued with a short break on Sunday for five days, increasing in violence and gradually becoming colder and more charged with snow until yesterday, when we had a thick overcast day with falling and driving snow and temperature down to −11°.

Went beyond Castle Rock on Sunday and Monday mornings with Griffith Taylor.

Think the wind fairly local and that the Strait has frozen over to the north, as streams of drift snow and ice crystals (off the cliffs) were building up the ice sheet towards the wind. Monday we could see the approaching white sheet—yesterday it was visibly closer to land, though the wind had not decreased. Walking was little pleasure on either Page:Scott's Last Expedition, Volume 1.djvu/341 day: yesterday climbed about hills to see all possible. No one else left the hut. In the evening the wind fell and freezing continued during night (min.−17°). This morning there is ice everywhere. I cannot help thinking it has come to stay. In Arrival Bay it is 6 to 7 inches thick, but the new pools beyond have only 1 inch of the regular elastic sludgy new ice. The sky cleared last night, and this morning we have sunshine for the first time for many days. If this weather holds for a day we shall be all right. We are getting towards the end of our luxuries, so that it is quite time we made a move—we are very near the end of the sugar.

The skuas seem to have gone, the last was seen on Sunday. These birds were very shy towards the end of their stay, also very dark in plumage; they did not seem hungry, and yet it must have been difficult for them to get food.

The seals are coming up in our Bay—five last night. Luckily the dogs have not yet discovered them or the fact that the sea ice will bear them.

Had an interesting talk with Taylor on agglomerate and basaltic dykes of Castle Rock. The perfection of the small cone craters below Castle Rock seem to support the theory we have come to, that there have been volcanic disturbances since the recession of the greater ice sheet.

It is a great thing having Wright to fog out the ice problems, and he has had a good opportunity of observing many interesting things here. He is keeping notes of ice changes and a keen eye on ice phenomena; we have many discussions.

Yesterday Wilson prepared a fry of seal meat with penguin blubber. It had a flavour like cod-liver oil and was not much appreciated—some ate their share, and I think all would have done so if we had had sledging appetites—shades of Discovery days!!16

This Emperor weighed anything from 88 to 96 lbs., and therefore approximated to or exceeded the record.

The dogs are doing pretty well with one or two exceptions. Deek is the worst, but I begin to think all will pull through.

Thursday, April 6, a.m.—The weather continued fine and clear yesterday—one of the very few fine days we have had since our arrival at the hut.

The sun shone continuously from early morning till it set behind the northern hills about 5 p.m. The sea froze completely, but with only a thin sheet to the north. A fairly strong northerly wind sprang up, causing this thin ice to override and to leave several open leads near the land. In the forenoon I went to the edge of the new ice with Wright. It looked at the limit of safety and we did not venture far. The over-riding is interesting: the edge of one sheet splits as it rises and slides over the other sheet in long tongues which creep onward impressively. Whilst motion lasts there is continuous music, a medley of high-pitched but tuneful notes—one might imagine small birds chirping in a wood. The ice sings, we say.

P.M.—In the afternoon went nearly two miles to the north over the young ice; found it about 3½ inches thick. At supper arranged programme for shift to Cape Evans—Photo of a small tabular iceberg in open water, with penguins on shore in the foreground
A Berg Drifting in McMurdo Sound

Photo of thin, angular patches of ice largely covering over a bay
Pancake Ice Forming into Floes off Cape Evans
men to go on Saturday—dogs Sunday—ponies Monday—all subject to maintenance of good weather of course.

Friday, April 7.—Went north over ice with Atkinson, Bowers, Taylor, Cherry-Garrard; found the thickness nearly 5 inches everywhere except in open water leads, which remain open in many places. As we got away from the land we got on an interesting surface of small pancakes, much capped and pressed up, a sort of mosaic. This is the ice which was built up from lee side of the Strait, spreading across to windward against the strong winds of Monday and Tuesday.

Another point of interest was the manner in which the overriding ice sheets had scraped the under floes.

Taylor fell in when rather foolishly trying to cross a thinly covered lead—he had a very scared face for a moment or two whilst we hurried to the rescue, but hauled himself out with his ice axe without our help and walked back with Cherry.

The remainder of us went on till abreast of the sulphur cones under Castle Rock, when we made for the shore, and with a little mutual help climbed the cliff and returned by land.

As far as one can see all should be well for our return to-morrow, but the sky is clouding to-night and a change of weather seems imminent. Three successive fine days seem near the limit in this region.

We have picked up quite a number of fish frozen in the ice—the larger ones about the size of a herring and the smaller of a minnow. We imagined both had been driven into the slushy ice by seals, but to-day Gran found a large fish frozen in the act of swallowing a small one. It looks as though both small and large are caught when one is chasing the other.

We have achieved such great comfort here that one is half sorry to leave—it is a fine healthy existence with many hours spent in the open and generally some interesting object for our walks abroad. The hill climbing gives excellent exercise—we shall miss much of it at Cape Evans. But I am anxious to get back and see that all is well at the latter, as for a long time I have been wondering how our beach has withstood the shocks of northerly winds. The thought that the hut may have been damaged by the sea in one of the heavy storms will not be banished.

A Sketch of the Life at Hut Point

We gather around the fire seated on packing-cases, with a hunk of bread and butter and a steaming pannikin of tea, and life is well worth living. After lunch we are out and about again; there is little to tempt a long stay indoors, and exercise keeps us all the fitter.

The failing light and approach of supper drives us home again with good appetites about 5 or 6 o'clock, and then the cooks rival one another in preparing succulent dishes of fried seal liver. A single dish may not seem to offer much opportunity of variation, but a lot can be done with a little flour, a handful of raisins, a spoonful of curry powder, or the addition of a little boiled pea meal. Be this as it may, we never tire of our dish and exclamations of satisfaction can be heard every night—or nearly every night; for two nights ago [April 4] Wilson, who has proved a genius in the invention of 'plats,' almost ruined his reputation. He proposed to fry the seal liver in penguin blubber, suggesting that the latter could be freed from all rankness. The blubber was obtained and rendered down with great care, the result appeared as delightfully pure fat free from smell; but appearances were deceptive; the 'fry' proved redolent of penguin, a concentrated essence of that peculiar flavour which faintly lingers in the meat and should not be emphasised. Three heroes got through their pannikins, but the rest of us decided to be contented with cocoa and biscuit after tasting the first mouthful. After supper we have an hour or so of smoking and conversation—a cheering, pleasant hour—in which reminiscences are exchanged by a company which has very literally had world-wide experience. There is scarce a country under the sun which one or another of us has not travelled in, so diverse are our origins and occupations. An hour or so after supper we tail off one by one, spread out our sleeping-bags, take off our shoes and creep into comfort, for our reindeer bags are really warm and comfortable now that they have had a chance of drying, and the hut retains some of the heat generated in it. Thanks to the success of the blubber lamps and to a fair supply of candles, we can muster ample light to read for another hour or two, and so tucked up in our furs we study the social and political questions of the past decade.

We muster no less than sixteen. Seven of us pretty well cover the floor of one wing of the L-shaped enclosure, four sleep in the other wing, which also holds the store, whilst the remaining five occupy the annexe and affect to find the colder temperature more salubrious. Everyone can manage eight or nine hours' sleep without a break, and not a few would have little difficulty in sleeping the clock round, which goes to show that our extremely simple life is an exceedingly healthy one, though with faces and hands blackened with smoke, appearances might not lead an outsider to suppose it.

Sunday, April 9, a.m.—On Friday night it grew overcast and the wind went to the south. During the whole of yesterday and last night it blew a moderate blizzard—the temperature at highest +5°, a relatively small amount of drift. On Friday night the ice in the Strait went out from a line meeting the shore ¾ mile north of Hut Point. A crack off Hut Point and curving to N.W. opened to about 15 or 20 feet, the opening continuing on the north side of the Point. It is strange that the ice thus opened should have remained.

Ice cleared out to the north directly wind commenced—it didn't wait a single instant, showing that our journey over it earlier in the day was a very risky proceeding—the uncertainty of these conditions is beyond words, but there shall be no more of this foolish venturing on young ice. This decision seems to put off the return of the ponies to a comparatively late date.

Yesterday went to the second crater, Arrival Heights, hoping to see the condition of the northerly bays, but Page:Scott's Last Expedition, Volume 1.djvu/351 Page:Scott's Last Expedition, Volume 1.djvu/352 Page:Scott's Last Expedition, Volume 1.djvu/353 Page:Scott's Last Expedition, Volume 1.djvu/354

Freezing of Bays. Cape Evans

March 15.—General young ice formed.

March 19.—Bay cleared except strip inside Inaccessible and Razor Back Islands to Corner Turk's Head.

March 20.—Everything cleared.

March 25.—Sea froze over inside Islands for good.

March 28.—Sea frozen as far as seen.

March 30.—Remaining only inside Islands.

April 1.—Limit Cape to Island.

April 6.—Present limit freezing in Strait and in North Bay.
April 9.—Strait cleared except former limit and some ice in North Bay likely to remain.

  1. I.e. by land, now that the sea ice was out.
  2. Because the seals would cease to come up.
  3. As a step towards 'getting these things clearer' in his mind two spare pages of the diary are rilled with neat tables, showing the main classes into which rocks are divided, and their natural subdivisions—the sedimentary, according to mode of deposition, chemical, organic, or aqueous; the metamorphic, according to the kind of rock altered by heat; the igneous, according to their chemical composition.