Scientific Intelligence. — Meteorology. 419 



bable that Beresow is near the limit of perpetual ground-ice. 

 Farther east, this frozen soil extends much more to the south- 

 ward, even to the shores of the lake Baikal ; indeed, the whole 

 of the south-eastern angle of Siberia has perpetual ground- 

 ice. Captain Frehre states that, in 1836, he there found the 

 ground frozen at some distance below the surface, and that this 

 frozen stratum was continued uninterruptedly quite to the un- 

 derlying rock, to a depth of from 10 feet to 40 feet. But, as he 

 always found rock there, it would be difficult to say how thick 

 the layer of frozen mud would be in the lat. of 52°. It thawed 

 on the surface of the banks of the river, to a depth of from 

 2J feet to 6 feet, and from 6 feet to 9 feet on the naked heights ; 

 but, in the forests, where the rays of the sun were intercepted, 

 the thaw reached only from | foot to 1 foot deep. If it be true 

 that there are places in forests where the ground is never thaw- 

 ed one foot deep, it would demonstrate how little is necessary 

 for the ground to be thawed for trees to grow on it. The de- 

 velopment of the leaves and vegetation depends less on the tem- 

 perature of the soil than on that of the air in the spring ; it on- 

 ly requires that the ground should be so far thawed that the 

 tree may be able to draw from it a sufficient quantity of mois- 

 ture for its growth.*"" 



3. On the Aurora Borealis. — When in our climates, the au- 

 rora borealis is complete, — when one part of its light pictures 

 on space a well-defined arch, the culminating' point of this 

 ARCH is in the magnetic meridian, and its two points of appa- 

 rent intersection with the horizon are at equal angular distances 

 from the same meridian. 



When it projects luminous columns from different portions 

 of the arch, their point of intersection^ called by certain meteo- 

 rologists the ceiitre of the cupola, is found in the magnetic meri- 

 dian, QXidi precisely upon the prolongation of the dipping needle. 



It is very important to repeat these kind of observations ; 

 and less with the object of establishing between the aurora bo- 



• Mr De la Beche remarked, that, considered geologically, this paper of 

 Prof. Baer was an important one. It shewed that the temperature of those 

 regions hud changed since the deposit of the dctrital matter (for that was the 

 character of the frozen ground), inasmuch as, under the condition of a perpe- 

 tually frozen surface, no such deposits could take place. 



