306 ANNUAL OF SCIENTIFIC DISCOVERY. 



Stream and Gulf of Mexico, and that this Greensand is often in the form of 

 well-defined casts of Polythalamia, minute Mollusks, and branching Tubuli ; 

 and that the same variety of petrifying material is found as in the fossil casts, 

 some Toeing well-defined Greensand, others reddish, brownish, or almost white. 

 In some cases I have noticed a single cell, of a spiral Poly thalamian cast, to 

 be composed of Greensand, while all the others were red or white, or vice 

 versa. 



The species of Polythalamia whose casts are thus preserved, are easily 

 recognizable as identical with those whose perfectly preserved shells form the 

 chief part of the soundings. That these are of recent species is proved by 

 the facts that some of them still retain their brilliant red coloring, and that 

 they leave distinct remains of their soft parts when treated with dilute acids. 

 It is not to be supposed, therefore, that these casts are of extinct species 

 washed out of ancient submarine deposits. They are now forming in the 

 muds as they are deposited, and we have thus now going on in the present 

 seas a formation of Greensand by processes precisely analogous to those 

 which produced deposits of the same material as long ago as the Silurian 

 epoch. In this connection it is important to observe" that Ehrenberg's 

 observations, and my own, establish the fact that other organic bodies than 

 Polythalamia produce casts of Greensand, and it should also be stated that 

 many of the grains of Greensand accompanying the well-defined oasts are of 

 wholly unrecognizable forms, having merely a rounded, cracked, lobed, or 

 even coprolitic appearance. Certainly many of these masses, which often 

 compose whole strata, were not formed either in the cavities of Polythalamia 

 or Mollusks. The fact, however, being established beyond a doubt, that 

 Greensand does form casts in the cavities of various organic bodies, there 

 is a great probability that all the masses of this substance, however irregular, 

 were formed in connexion with organic bodies, and that the chemical changes 

 accompanying the decay of the organic matter have been essentially connected 

 with the deposits in the cavities, of green and red silicates of iron, and of 

 nearly pure silica. It is a curious fact in this connection, that the siliceous 

 organisms, such as the Diatomaceas, Polycistinese, and Spongiolites, which 

 accompany the Polythalamia in the Gulf Stream, do not appear to have any 

 influence in the formation of casts. 



The discovery by Prof. Ehrenberg of the connection between organic bodies 

 and the formation of Greensand, is one of very great interest ; and is one of 

 the many instances which he has given to prove the extensive agency of the 

 minutest beings in producing geological changes. 



HEIGHT OP THE HTM AT. AY AS. 



It appears from a late survey made of the Himalaya range, by Colonel 

 Waugh, that the Khanchinjinga, which has been hitherto supposed to be the 

 highest summit, is in fact not so a higher mountain having been discovered, 

 situated between Katamandoo and Khanchinjinga. This last named is 28,156 

 feet above the level of the sea ; but the new summit reaches the enormous 

 height of 29,002 feet. It has been proposed to call this Mount Everest, after 

 a former surveyor-general of India. 



