EHRENBERG ON INFUSORIA IN IGNEOUS ROCKS. 83 



" Notwithstanding that the whole thickness of the deposit has not 

 been penetrated at this point, there is no doubt that the series of 

 deposits upon the grauwacke consists exclusively of various conglo- 

 merates and tuffs of volcanic origin, having very different thickness, 

 and containing, interstratified with them, several infusorial masses ; 

 and the whole sequence is essentially identical with the very similar 

 series in the neighbourhood of the Laacher-See." 



The microscopic investigation of the thirty-nine specimens for- 

 warded has led to the following results : — 



1. The whole stratified deposit of volcanic tuff and conglomerate 

 reposing on the grauwacke at Hochsimmer, just as in the case of 

 the Brohl Valley, and the similar masses on the east bank of the 

 Rhine (e. g. the pumiceous conglomerate or sandstone of Engers), 

 air exhibit relations with minute organic life, and are often, to all 

 intents and purposes, actually formed of microscopic animalcules. 



The relation with organic beings is of this kind : not only are 

 there complete layers of distinctly recognisable organic bodies, which 

 were once the siliceous cases of infusorial animalcules, but, with few 

 exceptions, every fragment of tuff not larger than a pin's head will 

 be found to contain several portions, sufficiently preserved to enable 

 us to identify specific forms, and often exhibit complete shells of these 

 minute beings ; sometimes also the whole mass is almost entirely 

 made up of them. 



In the rock at Brohl and the firestone of Bell, it is the included 

 pumice which exhibits remains of this kind either complete or in a 

 fragmentary state ; and in the pumiceous conglomerate, or, as it is 

 called, the sandstone of Engers, it is not the grey interstratified mass, 

 but the white pumice-like nucleus of the conglomerate, which also 

 here and there contains similar organic bodies though in a fragmen- 

 tary condition. Many of these in the regular volcanic tuff' forma- 

 tions appear to have become quite unrecognisable ; but amongst the 

 mass some may often be found which enable us to determine both 

 the genus and species of the little animalcule of which they are the 

 remains. 



In most of these volcanic tuffs one may often perceive, by using 

 transmitted light, green, brown or white crystals, of which the green 

 are for the most part columnar, oblique-rhomboidal, acutely-pointed 

 prisms, appearing black Avith refiected light, being in all probability 

 crystals of augitc, while the obtuse brown crystals are more likely 

 to be hornblende. Many of the tuffs contain great quantities of 

 exceedingly small white transparent crystals in which sometimes tliere 

 may be distinctly traced the rhombic-dodecahcdral form, and these 

 no doubt are sodalitc, or perhaps occasionally leucite. 



2. The masses thus characterized appear to be, as tliey have al- 

 ways been considered, of volcanic origin. The numerous small cry- 

 stals of augito which make up so large a part — often at least one-half 

 of tiie whole mass — and those white kernels and particles of sodalitc 

 and leucite visible to the naked eye, have hitherto been considered 

 as the result of the action of heat, since we arc not aware of the 

 possibility of such forms of the mineral being producible by aqueous 



