28 THE POPULAR SCIENCE MO^^THLY. 



in the years 1836-39. Ehrenberg, in fact, had shown that the exten- 

 sive beds of " rotten-stone " or " Tripoli " which occur in various parts 

 of the world, and notably at Bilin in Bohemia, consisted of accumula- 

 tions of the silicious cases and skeletons, Diatomacem, sponges, and 

 HacUolaria ; he had proved that similar deposits were being formed 

 by Dlatomacece in the pools of the Tliiergarten, in Berlin and else- 

 where, and had pointed out that, if it were commercially worth while, 

 rotten-stone might be manufactured by a process of diatom-culture. 

 Observations, conducted at Cuxhaenv in 1839, had revealed the exist- 

 ence, at the surface of the waters of the Baltic, of living diatoms and 

 Madiolaria of the same species as those w^hich, in a fossil state, con- 

 stitute extensive rocks of Tertiary age at Caltanisetta, Zante, and 

 Oran, on the shores of the Mediterranean. 



Moreover, in the fresh-water rotten-stone beds of Bilin, Ehrenberg 

 had traced out the metamorphosis, effected apparently by the action 

 of percolating water, of the primitively loose and friable deposit of 

 organized particles, in which the silex exists in the hydrated or solu- 

 ble condition. The silex, in fact, undergoes solution and slow rede- 

 position, until, in ultimate result, the excessively tine-grained sand, 

 each particle of which is a skeleton, becomes converted into a dense 

 opaline stone, with only here and there an indication of an organism. 



From the consideration of these facts, Ehrenberg, as early as the 

 year 1839, had arrived at the conclusion that rocks, altogether similar 

 to those which constitute a large part of the crust of the earth, must 

 be forming, at the present day, at the bottom of the sea ; and he 

 threw out the suggestion that even where no traces of organic struct- 

 ure is to be found in the older rocks, it may have been lost by meta- 

 morjjhosis.* 



The results of the antarctic exploration, as stated by Dr. Hooker 

 in the " Botany of the Antarctic Voyage," and in a paj^er which he 

 read before the British Association in 1847, are of the greatest im- 

 portance in connection with these views, and they are so clearly stated 

 in the former work, which is somewhat inaccessible, that I make no 

 apology for quoting them at length : 



" The waters and the ice of the South Polar Ocean were alike found to 

 abound with microscopic vegetables belonging to the order DiatomacecB. Though 

 much too small to be discernible by the naked eye, they occurred in such count- 

 less myriads as to stain the berg and the pack-ice wherever tliey were washed 

 by the swell of the sea ; and, when inclosed in tlie congealing surface of the 

 water, they imparted to the brash and pancake-ice a pale ochreous color. In 

 the open ocean, northward of the frozen zone, this order, though no doubt al- 



' " Ueber die noch jetzt zahlreich lebenden Thierarten der Kreidebildung und den 

 Organismus der Polytbalamien," Abhandlungen der Koniglichen Akademie der Wissen- 

 schaften, 1839. Berlin, 1841. I am afraid that this remarkable paper has been some- 

 what overlooked ia the recent discussions of the relation of ancient rocks to modern 

 deposits. 



