In addition to the several arduous journeys performed by this intrepid traveller and his companions, many questions hitherto unsolved were investigated and much new light added to our previous knowledge on these respective points. One was the real state of the question of the frozen subsoil of Siberia. "By placing thermometers at various depths in the shaft at Yakutsk, he has found that at its bottom, or at 382 feet below the surface, the cold is 2° 4´´ Réaumur, and that it is probable the frozen subsoil reaches to the great depth of about 600 feet! Notwithstanding this extraordinary phenomenon, the lateral extent of which has still to be determined, it appears that the culture of rye succeeds perfectly under favorable local conditions in those regions, and that the crops of grain are more abundant than in Livonia!" M. Middendorff has also thrown new light on the boreal range of vegetation. He has ascertained "that whilst rye, turnips, beets, and potatoes grow on the Yenisei to latitude 61° 40´, indigenous plants, requiring less warmth, flourish much farther north, and that even trees with vertical stems reach to about 72° north latitude, in that parallel of longitude!" This fact will show that geographers can no longer mark the limit of vegetation by a rectilinear zone, but must accommodate such line to climatological and local conditions. In regard to the mammoths, the fossil bones of which have been found in Siberia, M. Middendorff has shown that, in accordance with the views of Professor Owen, (who states that these quadrupeds were specially organized to live on the branches and leaves of such shrubs and trees as grow in boreal latitudes) there are still trees in latitude 72° which would suffice for their sustenance. The Ethnology of this region has been elucidated by our traveller, who by investigating the languages and physical characteristics of these remote tribes, has been enabled to affiliate them with their parent stocks. Our knowledge of the geology and geography of the northern and southeastern extremities of Siberia have been greatly extended by this journey; in fact no enquiry for the advancement of science and a knowledge of this far distant and hitherto unknown region, seems to have been neglected.[95] Another scientific expedition of an Ethnological character is employed in Siberia under the direction of M. Castren, who has devoted much of his first report to the geography of the country. After speaking of the river Irtisch and its fisheries, he gives some account of the Ostiaks, the most ancient people of its banks. Surrounded by Russians and Tartars, they have lost all their nationality except their language. The Tartar influence is feeble, but that of Russia is felt in their religion, their manners, their customs and even in their general mode of thinking.