making lime. At another locality about eight or ten miles up the Big Sioux river, which comes in from the northwest, one of us (Dr. H.) saw No. 1, containing its characteristic fossil leaves, directly beneath No. 2, of the Nebraska section. The exposure presented the following beds in the descending order: 1. 20 feet exposed of light gray limestone and 3. 15 feet exposed above the edge of the water, } No. 3, Nebraska Sec. No. 2, Nebraska Sec. a thin bed of impure lignite above, and some No. 1, Nebraska Sec. layers of various colored clay below, containing dicotyledonous leaves. One of the sketches of a long lanceolate leaf, like some of the existing species of Salix, sent by us to Prof. Heer, was drawn from a specimen collected from one of the lower sandstones here. Again at another locality on the Missouri, about thirty miles above the mouth of Big Sioux river, No. 1, was seen by one of us (Dr. H.) only five feet above the water's edge, and immediately overlaid by No. 2, of the Nebraska section, containing its characteristic species of Ammonites; and directly over the latter, he saw No. 3, containing Inoceramus problematicus.* At this locality he also found in No. 1 some of the same fossil leaves that characterize it at the other places already mentioned. On ascending the Missouri, above the last named locality, formations No. 2, 3, 4 and 5 are seen to sink at the same gradual uniform rate of dip, in regular succession, beneath the level of the river; so that on reaching Heart river, we find the top of No. 5 nearly down on a level with the water's edge, and a short distance above that locality, it passes out of sight to be succeeded by the Great Tertiary Lignite basin of the upper Missouri, which overlaps it on the hills along the river for some distance below. From the foregoing statement, we think it will be clearly understood, that formation No. 1 of the Nebraska section holds. a position beneath the other cretaceous deposits of that region; while the occurrence in it of the remains of highly organized angiosperm dicotyledonous plants proves that it cannot be older than Cretaceous. It may be argued, however, that it may in part be Cretaceous and part Tertiary, or at any rate that some of these leaves may have been obtained from overlying Tertiary beds which we have confounded with the Cretaceous below. *It is of course unnecessary for us to inform geological readers that a rock overlaid by strata containing Ammonites and Inoceramus, cannot be Tertiary because these genera became extinct at the dawn of the Tertiary epoch. This, however, is impossible, simply because specimens of nearly all the species found at the various localities have been quarried from the same bed at Blackbird Hill, and the whole,-not a part only-of this formation, passes beneath all the other Cretaceous rocks of the northwest. In addition to this, we have extensive collections of plants from the Tertiary of Nebraska, not a single species of which is identical with those from No. 1. When we stated in some of our papers that it was possible we might have included in this formation beds not belonging to the Cretaceous, it was not because we thought any part of it might be Tertiary, but because we suspected some of the lower beds referred to it in Kansas might possibly be Jurassic; and we are even now prepared to believe that it may yet be found to repose on Jurassic rocks in that Territory, as it does at the Black Hills, in Nebraska. ART. XXVIII.-Geographical Notices. No. VI. SEMENOW'S EXPLORATIONS IN CENTRAL ASIA, 1857.-The trigonometrical survey of India, the exploring expedition of the Brothers Schlagintweit, and the researches of Russian travellers are making valuable contributions to our knowledge of Central Asia. In a recent number of Petermann's journal a highly important paper is presented in respect to the expedition of P. V. Semenow, in the neighborhood of the Balkasch lake. The article is based upon original data furnished by the traveller, and dated St. Petersburg, June, 1858. We condense and translate such portions of the article as are most interesting, regretting that we are not able to transfer it entire. To the south of the Russo-Siberian frontier and military post route, which follows the course of the Irtysh, there extends a wide and sterile tract, universally known as the Kirghese Steppe. This Steppe has a rocky substratum mostly crystalline, but in part also sedimentary, swelling into hills and occasionally aggregated into small and low mountain-clusters. Its characteristic features are aridity, the absence of trees, scarcity of streams, relatively insignificant height of the hills which hardly in a single instance deserve the name of mountains, and numerous saltdeserts with their accompanying halophytes (salt water plants). But as we arrive at the river Ajagus, an eastern tributary of the Balkhash Lake, and pass beyond the low sandy downs, that by their depression, their saline character, and their numerous standing pools bordered with sedges, indicate a former connection between the Balkhash and the Ala-kul, we enter an entirely different region. This long low mostly dry bed of what must formerly have been one continuous lake extending from the 74th to the 82d meridian east of Greenwich, forms a marked dividing line between the mountain-systems and general physical features of Central Asia on the south, and Siberia on the north. From this line onward we encounter a continuous series of magnificent Alp-lands, rising height above height till they at last blend with the Thian-schan, the most central of the mountain ranges of Asia. This line too forms a natural limit, north of which we no longer find many of the vegetable growths or the animals of Central Asia, such for instance as the Populus diversifolia and the Pyrus Sieversiana among trees, or the tiger, the hedgehog, the pheasant, &c., among animals. Semenow's explorations, made in the year 1857, relate mostly to this Central Asiatic Alp-land, which though comparatively small in extent, is yet charming for the variety of its scenery, and attractive to the physical geographer for its union of so many different zones with their diverse characteristics of soil, of temperature, of vegetable and animal species, etc. It is bounded on the north as we have stated by the Balkasch-Ala-kul Lake belt, on the east by the snow-covered crest of the Dzungarisch Ala-tau, and on the south by the perpetual snows and glaciers of the Thian-schan, and it comprises all altitudes between the wide extremes of 600 and 2000 Paris feet.* This region, in addition to its interest for natural science, is also attractive to the ethnographer, as having been from the earliest times one of the most important stations for those vast wandering hordes which have successively overrun Europe. For here in the broad and fertile valley of the Ili they would often stop for several years, and then with the fresh strength and energy gained by their repose, take up their march around the southern shore of the Balkhasch, either northwest toward Europe, or southwest towards Turan, Southern and Western Asia. The Ili divides this portion of Central Asia into two parts, the northern called "the land of seven rivers," the southern "the land across the Ili," (Transilian,) names given them by the early Russian settlers. The distinctive features of this region are its three lofty Alplands, viz.: 1. The Dzungarisch Ala-tau, (closely connected with the Talki-chain that divides the Ala-kul and the Ili valleys,) with a medium ridge altitude of 6,000 feet, and a peak altitude of 12,000 feet. 2. "The Ala-tau across the Ili," between the Ili valley and the Issyk-kul plateau, with a medium ridge altitude of 8000 feet, and a peak altitude of not far from 14,000 to 15,000 feet; and * Semenow's measurements are all given in Paris feet. 3. The Thian-schan, between the Issyk-kul plateau and the plains of Little Bucharest, with a medium ridge altitude of about 11,000 feet, and a peak altitude of perhaps 20,000 feet. The Dzungarish Ala-tau on its western slope and the Transilian Alatau on its northern face decline directly into a broad Steppe-level that stretches away at the varying elevation of 1500 to 500 feet to the Balkasch basin, and comprises the entire western and northwestern portion of this region. And the nearer we approach to the Balkasch, the more flat, arid, unfruitful, sandy and saline does the soil appear, gradually becoming covered with the Haloxylon ammodendron and with halophytes; and the streams, which as they issued from the mountains were bright, clear and rapid, become more sluggish and turbid till at last they come to a stand amidst sandy downs and sedgy marshes, and but three of them, viz.: the Lepsa, the Karatal, and the Ili actually reach the Balkasch Lake. But the transition zone between the mountain-land and this Steppe, is on the contrary, one of the finest agricultural tracts on the continent. It possesses a deep vegetable mould, a luxurious growth and such an abundance of water that the inhabitants, the Kirghese, the Buruti and the Russian Cossacks, apply an artificial irrigation to their fields with surprising facility. If we now take a general survey of this region in its practical adaptations to the wants of its inhabitants we shall find that it includes four natural zones, each offering its peculiar tribute to the general welfare. 1. The Steppe-zone, 500 to 1500 and in some places 2,000 feet above sea-level, affords most excellent winter quarters for the Nomads, on account of its mild climate. and its almost entire exemption from snow. 2. The agricultural zone, from 1,500 to 4,000 feet of altitude, contains rich arable lands. 3. The pine-tree zone, from 4,000 to 7,000 feet in altitude, yields abundance of timber wood for building; and 4, the Alpine meadow zone, from 7,600 to 9,000 feet in altitude, entices the Nomads by its wholesome air and its rich pasturage to resort thither during the summer. There are two other zones, viz.: the High-Alp and glacier-zone from 9,000 to 11,200 feet in altitude, with its brilliant flora, and the snow-zone, or the region of perpetual snow; but these will forever remain practically of no immediate importance to colonists. We omit Semenow's measurements and notes, geological, physical and enthusiastically descriptive, taken during his explorations in the Dzungarisch Ala-tau and the Thian Schan, and give briefly the results of his observations upon the Issyk-kul lake. Between the Transilian Ala-tau and the Thian-schan ranges there is a plateau of 4,200 feet altitude, 230 wersts in length, and 70 in breadth, in which the charming lake of Issykkul is situated. This lake is 150 wersts in its extreme length by SECOND SERIES, VOL. XXVII, No. 80.-MARCH, 1859. 50 wersts in breadth. Its waters are brackish and unpalatable. It is fed by over 40 short mountain streams, which fertilize the otherwise sterile soil of the plateau, and which are fringed by long lines of trees. But little sedge is to be met with, and that only around the indentations of the lake. On the contrary, the Hippophae rhamnoides forms a thick bushy growth in the neighborhood of the shore. Between the mountains and the lake there is a belt of from 7 to 20 wersts in breadth. At one point only do we find the case otherwise, viz.: the Kesse Tsengyr on the northern shore, where a spur from the Ala-tau approaches so near the water that there is merely room enough left for a waggon road. The immediate border of the lake is in general low and sandy; but around some of the bights the land is more elevated and presents a steep descent to the water; in such places the beating of the waves frequently wears away the loose alluvial strata of which these bluffs consist, so that large masses will at intervals crumble into the lake. Semenow saw no islands in the Issyk-kul. From the fact that so many streams flow into it, he conjectured that it must at some point effect an outlet. Geographers had hitherto represented the river Tschu as such an outlet, but Semenow followed the Tschu up toward its source and ascertained that it approached the lake no nearer than 5 wersts. Here it breaks through a frightful gorge in the Byam mountain, a continuation of the Transilian Ala-tau, and flows N.E. to unite with the Kebin. If the waters of the Issykkul had at some previous period been about two hundred feet higher than they now are, (and there are water-marks near the base of the mountain which may warrant such a supposition,) then the lake may itself have opened the Byam gorge, and so discharged its surplus flood into the Tschu. Such a former high state of its waters will account for the frequent conglomerate strata on its banks, which were doubtless formed in the lake-bed, and brought to view on the recession of the waters. Semenow found moreover an additional argument for this hypothesis in a legend of the Buruti that the ruins of a submerged city are at certain seasons visible at the mouth of the Tub, and under the surface of the water. In fine his explorations led him to conclude that if it were not for the existence of the Byam gorge, there is no good reason why the Issyk-kul might not rise not merely 200 feet but many hundred feet above its present level. It only remains for us now to speak of the temperature of the Issyk-kul plateau. Near Viernoie, the second Russian settlement on the military road to the Transilian Ala-tau, and directly to the north of these mountains, the ground is commonly cov ered with snow only in January and February. In the Issykkul plateau snow lies on the ground for over four months of the winter season. In the beginning of May when at Viernoie, |