360 ANNUAL OF SCIENTIFIC DISCOVERY. 



and becomes at length so strong as to crystallize when evaporated to a suffi- 

 cient extent. It appears the salts contained in these lake waters arc used in 

 the neighborhood for the manufacture of soap, and Mr. Loftus is of opinion 

 if it were not for the great expense of transport they might be profitably 

 brought to England, where there are many important uses for these various 

 salts of soda. 



At present the material would have to be taken by land carriage over 

 seventy miles of sandy country, destitute of roads, in order to reach the Cas- 

 pian Sea, and this operates as a complete bar to any commercial speculation 

 in the matter. 



THE THEOEY OF GLACIERS. 



The interesting phenomena presented by the glaciers of the Alps have of 

 late occupied much attention among scientific men. One chief point of dif- 

 ficulty is, to account for the existence, in the white porous mass of the gla- 

 cier, of lamina?, or streaks of blue ice, of superior density to the rest. Pro- 

 fessor James Forbes of Edinburgh has offered a theory to account for this ap- 

 pearance, which has been hitherto generally accepted in the scientific world. 

 He supposes that ice is in a viscous, or, as he sometimes expresses it, a semi- 

 fluid state when in motion. The friction at the sides of the glacier prevents 

 its lateral portions from moving with the same velocity as the central. Fis- 

 sures are supposed to be formed in consequence of this differential motion. 

 The drainage water from the surface is next supposed to flow into these fis- 

 sures, to become frozen there, and thus to form the blue lamina?. The ex- 

 planation of the directions in which the lamina? run in different parts of the 

 glacier is founded upon known laws of motion into which it is needless for 

 us now to enter. 



In a lecture delivered at the Royal Institution, and in a paper read at the 

 Royal Society, Professor Tyndall, in conjunction with Professor Huxley, 

 has advanced a new theory. The idea that ice is viscous, he regards as a 

 conjecture opposed to common experience. The supposition that the blue 

 veins are formed by the drainage water, he rejects, and refers the lamination 

 of the glacier to the same general principle, which he has already proved to 

 be the cause of the lamination of slate rocks. This principle he illustrates 

 by pounding a common slate into an impalpable powder, mixing it wiih 

 water, and then subjecting it to pressure. It splits at right angles to the line 

 of pressure, just like the original slate from which it has been formed. 



Professor Tyndall tried the same experiment on snow. A quantity 

 of the substance subjected to pressiire exhibited on a small scale the struc- 

 ture of the glacier. 



The closing up of crevasses, and the establishment of the continuity of the 

 glacier after it has been broken into fragments in descending precipitous 

 slopes, are accounted for by reference to a principle for which the term " re- 

 gelation " has been suggested by Dr. Hooker. It is found that fragments 

 of ice, placed in contact in a hot sun, and even under boiling water, become 

 re-united, or frozen together. This fact, as Dr. Tyndall asserts, sufficiently 



