GEOLOGY. 219 



After stating that the Coccolitlis occur in all the soft mavis and 

 limestones of the Jurassic and liassic formations, "The Mus- 

 chelkalk," continues Dr. Giimbel, " appeared for a long time to be 

 proof against every experiment. Every specimen of marl which 

 I examined was apparently free from Coccolitlis. At last I had the 

 good fortune to discover traces of them in a somewhat impure 

 piece of rock-salt from Wilhemsgliick. Even here they show 

 themselves extremely sparingly, but in the company of flakes, 

 which are not unlike Batliybius. To the present time I have in 

 vain examined the similar rock-salts of Berchtesgaden and Stass- 

 furt ; and, as yet, indications of Coccolitlis in the Permian formation 

 and the coal-measures are wanting. On the other hand, the soft 

 marls of the mountain limestone of Regnitzlosan, the soft marls 

 of the Conodont strata of the Baltic provinces, the Trenton marl 

 of New York, and even the siliceous limestone of the Potsdam 

 sandstone, contain some traces, although to an extremely small 

 extent. 



" These facts all point to the conclusion that in the majority of 

 calcareous marine deposits the Coccolitlis originallyformed a more 

 or less essential part of the calcareous masses, and that, in thick 

 or granulous, and particularly ancient limestone rocks, they can 

 no longer be perceived, either on account of the opaque character 

 of the rocks, or because they have been made by some change 

 wholly or in part unrecognizable, or have been altogether de- 

 stroyed. I have been able by some experiments to throw further 

 light upon this subject. That these smallest organic bodies can 

 be recognized in hard limestones only in the rarest cases, even 

 when it contains them in great numbers, I convinced myself, by 

 means of thin slices, which I made from deep-sea mud, thoroughly 

 dried and rendered hard by repeated soaking in diluted Canada 

 balsam and heating, and also from writing-chalk, made hard 

 in the same way, and rich in Coccolitlis. The infinite numbers of 

 finest granules and rings are so massed together, one over the 

 other, "that it must be regarded as an extremely rare case when a 

 Coccolitli is clearly seen here and there at the very thinnest edges." 

 Nature, Nov. 3, 1870. 



THICKNESS OF GLACIERS. 



In his memoir " On the Mechanical Properties of Ice," pub- 

 lished in the "Philosophical Magazine" for January, 1870, Canon 

 Moseley arrives at a conclusion in regard to the crushing of ice, 

 to which I am unable, without some qualifications, to agree. In 

 his experiments ice was crushed under a pressure of 308.4 pounds 

 on the square inch, and he concludes that if a glacier is over 710 

 feet in thickness, the ice at the under surface must be crushed by 

 the incumbent weight. Professor Philips also made some experi- 

 ments on thy crushing of ice, and he came to the conclusion that 

 the height of a crushing column of ice is between 1,000 and 1,500 

 feet, and concluded also if a glacier were to exceed this in thick- 

 ness the ice would lose its solidity. (/See a paper on Glacial 



