406 Prof. Erman on the Structior, the Melting, 



immediately the passage over it to Cadilosaja. The crumbling of 

 the ice into upright flakes extends for about a verst from the 

 bank; and then begins the level glossy surface. We made a 

 magnetic observation on the lake, when we had reached a distance 

 of about ten versts from the shore at Posolskoi. The ice afforded 

 our instruments a perfectly firm foundation, and was at the same 

 time more free than any rock can be, from the suspicion of mag- 

 netic attraction. It is perfectly transparent, but traversed by 

 perpendicular cracks, by means of which we \\'ere enabled to dis- 

 cern whei-e the fluid and dark-green water began, and to esti- 

 mate the thickness of the ice at 4 feet. These cracks were all 

 extremely narrow, and filled only with air. Many of them 

 reached from the surface only to a certain depth, which was the 

 same for all, and seemed to be a third of the entire thickness of 

 the ice. The other cracks then began at this depth and reached 

 down to the water. I remarked, moreover, that the planes 

 which these cracks affect, intersect one another at an angle of 

 120°; so that both the upper and lower strata are thereby di- 

 vided into prisms, which have nearly the same kind of regularity 

 as basaltic columns, but with a much greater breadth. It was 

 evident that this separation must have taken place during the 

 congelation of the ice, and that this again took place at two dif- 

 ferent times, and instantaneously in each of the two strata alluded 

 to. It may be conceived that the uppermost layer of water 

 cooled down considerably below the freezing-point, and then 

 crystallized suddenly and in a mass. The lower stratum of ice 

 may have subsequently formed itself in precisely the same way, 

 its different age being proved by its different system of cracking. 

 Quite different in look and origin from the cracks here described 

 were the much wider fissures which are formed by the cooling 

 and contraction of the ice subsequent to its perfect congelation*, 

 I found one of these at the place where we were stojiping. It 

 ran from thence to the north-east and south-west with little de- 

 viation, to the horizon. It had throughout a uniform width of 

 4 inches, and reached from the upper surface to the water. It 

 was filled with new ice, which gave it the look of a vein or dyke 

 in rock. What added to this resemblance was, that the ice fiU- 



* Compare Reise um die Erde, u. s. w., Histor. Abth. vol. ii. p. 96. 

 Travels in Siberia, &c. vol. ii. p. 196. 



February 13. — We turned off from the western coast (of Baikal) directly 

 across the sea, till we made Posolskoi at the ojiposite side. There was no 

 snow upon the ice, so that its surface shone as a polished mirror. . . . The 

 regular and steady tread of our horses' feet rang over the wide and dreai-y 

 waste, interrupted now' and then by the shrill sound occasioned by the 

 sledges \\hcn they turned round and yielded at the same time to the 

 draught, or by the thiller noise emitted from the ice cracking under the in- 

 creasing severity of the frost. 



