The bridges, on the other hand, are very remarkable and numerous, and some of them required great skill in their construction, since they span the more important rivers of Siberia, which, with the exception of those in the basin of the Amur, invariably flow due north. There are four principal bridges, of which two cross the Irtysh and the Obi respectively, each 2,750 feet in length; the other two span the Yenissei and the Selenga, and are about 3,000 feet in length. These four bridges were exceedingly costly, necessitating the erection of stone piles of prodigious strength, capable of resisting the shock of the enormous masses of floating ice. The minor bridges, some of them 700 to 900 feet in length, are very numerous, but, beyond the difficulty of fixing them firmly a great distance on either side of the rivers, owing to the marshy nature of the soil on the immediate banks, it needed no superlative skill on the part of the engineers who superintended their erection. Altogether the most remarkable feature of the line will be the manner in which the trains are eventually to be transported across the Baikal, the largest lake in Asia. In America and in Denmark the system of running a train on to a monster ferry-boat, crossing considerable expanses of water, has now been in practical use for many years; but the distances hitherto have never exceeded seventy miles. The Toledo, Ann Harbour, and Northern Michigan Railroad possesses a service of ferry-boats that convey the trains across Lake Michigan, a distance of about seventy miles. The _Père Marquette_, the biggest ferry-boat in the world, so-called in honour of the celebrated Jesuit missionary and explorer, is 344 feet in length by 54 feet in width, and possesses four lines, whereby it can carry thirty freight cars and sixteen very up-to-date passenger corridor carriages. The difficulties to be surmounted with respect to Lake Baikal are happily less than those to be encountered on Lake Michigan. The distance from shore to shore, to begin with, is considerably less. Between Listvenitchnaya, otherwise the ‘Larches,’ to Misofsk is only forty miles. Notwithstanding the excessive cold, the Baikal does not freeze until quite late in January, on account of its great depth, 4,200 feet, of which 2,900 feet are below the level of the sea, forming a prodigious volume of water which takes a very long time to freeze, and an almost equally long time to thaw, for its temperature rarely rises, even in summer, above 5° C. During eight months of the year Lake Baikal is free and navigable, and it is believed that two crossings a day, always in the same channel, may eventually reduce the thickness of the ice in winter.