main lines of drainage, and slopes gradually towards the north.” The Seward Peninsula is particularly rugged. This great plateau drains westward through broad, gently flowing streams, the network of whose tributary waters penetrates every corner of the interior and offers easy means of communication. Both the main streams and the smaller tributaries often flow through deep canyons. The Yukon is one of the great drainage systems of the world. The Yukon itself has a length of more than 2000 m. and bisects the country from E. to W. Behind the bluffs that form in large part its immediate border its basin is a rolling country, at times sinking into great dead levels like the Yukon flats between Circle City and the Lower Ramparts, some 30,000 sq. m. in area. Of the two great affluents of the Yukon, the Tanana is for the most part unnavigable, while the Koyukuk is navigable for more than 450 m. by river steamers, and for more than 500 m. above its mouth shows no appreciable diminution in volume. A low water-parting divides the Yukon valley from the Kuskokwim, the second river of Alaska in size, navigable by steamers for 600 m. Torrential near its source, it is already a broad, sluggish stream at its confluence with the East Kuskokwim. The tides rise 50 ft. near its mouth and the tide-head is 100 m. above the mouth.
Rocky Mountains.—The Rocky Mountain system in Alaska is higher and more complex than in Canada. About 100 m. wide at the international boundary, where the peaks of the British Mountains on the N. and of the Davidson Mountains On the S. are 7000 to 8000 ft. high, the system runs W.S.W. as the Endicott Mountains, two contiguous ranges of about 5000 to 6000 ft., and as these ranges separate, the northern becomes the De Long, the southern the Baird Mountains, whose elevation rapidly decreases toward the coast-line. The system is sharply defined on the north and less so on the south.
Arctic Slope Region.—The Arctic Slope region is divided into the Anuktuvuk Plateau about 80 m. wide, with a maximum altitude to the S. of 2500 ft., and between the plateau and the Arctic Ocean the Coastal Plain. Very little is known of either part of the region.
Climate.—From the foregoing description of the country it is evident that the range of climate must be considerable. That of the coast and that of the Yukon plateau are quite distinct. The Panhandle, along with the lisière (foreland), westward to Cook Inlet might be called temperate Alaska, its climate being similar to that of the N.W. coast of the United States; while to the westward and northward the winters become longer and more severe. The cause of the mild climate of the Panhandle, formerly supposed to be the Japanese current, or Kuro Shiwo, is now held to be the general eastward drift of the waters of the North Pacific in the direction of the prevalent winds. To the warmth and moisture brought by this means the coastal region owes its high equable temperature, its heavy rainfall (80–110 in.) and its superb vegetation. The mean annual temperature is from 54° to 60° F. Winter sets in about the 1st of December and the snow is gone save in the mountains by the 1st of May. The thermometer rarely registers below zero F. or above 75° F.; the difference between the midwinter and midsummer averages is seldom more than 25°. The summer is relatively dry, the autumn and winter wet. The vapour-laden sea air blowing landward against the girdle of snow and glaciers on the mountain barriers a few miles inland drains its moisture in excessive rain and snow upon the lisière, shrouding it in well-nigh unbroken fog and cloud-bank. Only some 60 to 100 days in the year are clear. In passing from the Sitkan district westward toward Kodiak and the Aleutians (q.v.) the climate becomes even more equable, the temperature a little lower and the rainfall somewhat less;[1] the fogs at first less dense, especially near Cook Inlet, where the climate is extremely local, but more and more persistent along the Aleutians. The clear days of a year at Unalaska can be counted on the fingers; five days in seven it actually rains or snows. Bering Sea is covered with almost eternal fog. Along the coast N. of Alaska Peninsula the rainfall diminishes to 10 in. or less within the Arctic circle; the summer temperature is quite endurable but the winters are exceedingly rigorous.[2] East of the mountains in south-eastern Alaska the atmosphere is dry and bracing, the temperature ranging from −14° to 92° F. In the farther interior, in the valleys of the Yukon, the Tanana, the Copper and the Sushitna the summers are much the same in character, the winters much more severe. On the Yukon at the international boundary the mean of the warmest month is higher than that of the warmest month at Sitka, 500 m. southward. At some points in the Upper Yukon valley the range of extreme temperatures is as great as from −75° to 90° F.[3] The mean heat of summer in the upper valley is about 60° to 70° F., and at some points in the middle and lower valley even higher.[4] By the middle of September snow flurries have announced the imminence of winter, the smaller streams congeal, the earth freezes, the miner perforce abandons his diggings, and navigation ceases even on the Yukon in October. All winter snows fall heavily. The air is dry and quiet, and the cold relatively uniform. In midwinter in the upper valley the sun rises only a few degrees above the horizon for from four to six hours a day, though very often quite obscured. In December, January, February and March the thermometer often registers lower than −50° F., and the mean temperature is −20°. In May the rivers open, the cleared land thaws out, and by June the miner is again at work. Summer is quickly in full ascendancy. In May and June the sun shines from eighteen to twenty hours and diffused twilight fills the rest of the day. The rainfall is light, from 10 to 25 in. according to the year or the locality. Dull weather is unknown. All nature responds in rich and rapid growth to the garish light and intense heat of the long, splendid days. But the Alaska summer is the uncertain season at times the nights are cold into July, at times snow falls and there are frosts in mid-August; sometimes rain is heavy, or again there is a veritable drought. In the great river valleys S. of the Yukon basin climatic conditions are much less uniform.
Fauna and Flora.—The fauna of Alaska is very rich and surprisingly varied. The lists of insects, birds and mammals are especially noteworthy.[5] Of these three classes, and of other than purely zoological interest, are mosquitoes, which swarm in summer in the interior in vast numbers; sea fowl, which are remarkably abundant near the Aleutians; moose, and especially caribou, which in the past were very numerous in the interior and of extreme economic importance to the natives. The destruction of the wild caribou has threatened to expose the Indians to wholesale starvation, hence the effort which the United States government has made to stock the country with domestic reindeer from Siberia. This effort made under the direction of the Bureau of Education has been eminently successful, and in the future the reindeer seems certain to contribute very greatly to the food, clothing, means of shelter and miscellaneous industries of the natives; and not less to the solution of the problems of communication and transportation throughout the interior. It is, however, the fish and the fur-bearing animals of its rivers and surrounding seas that are economically most distinctive of and important to Alaska. The fishing grounds extend along the coast from the extreme south-east past the Aleutians into Bristol Bay. Herring are abundant, and cod especially so. There are probably more than 100,000 sq. m. of cod-banks from 22 to 90
- ↑ At Kodiak, the monthly means range from 28° to 55° with a total range from −10° to 82° F., as against −3° to 87° F. at Sitka; the average temperature is 40·6° F., rainfall 59 in.
- ↑ At St Michael the mean annual temperature is about 26°, the monthly means run from about −2° to 54°, and the extreme recorded temperatures from about −55° to 77° F.; at Port Clarence the annual mean is 22°, monthly means −7° to 51° F.; extreme range of temperature, −38° to 77° F.; at Point Barrow the annual mean is 7·7° F., monthly means −18·6° to 38·1°F., extreme range of temperature −55° to 65° F.
- ↑ The mean annual temperature on the Yukon at the international line is about 21° F., the monthly means run from −17° to 60° F., the range of extreme temperatures from −80° to 90° F.
- ↑ At Fort Yukon five years’ records showed mean seasonal temperatures of 14°, 60°, 17°, and −23·8° F. for spring, summer, autumn and winter respectively; at Holy Cross Mission 20°, 59°, 36° and 0·95°, at Nulato 29°, 60°, 36° and −14°.
- ↑ The Harriman expedition collected in two months 1000 species of insects, of which 344 species (and 6 genera) were new to science.
