90 DE. WALLICH ON THE PHYSICAL 



frequently than we find it ; there would have been no signs of the 

 specific contractility pertaining to colloidal silicic acid ; the result- 

 ing siliceous mineral instead of appearing, when not rendered cherty 

 by insoluble matter, as " a colloidal glassy hyalite,^' would have pre- 

 sented itself either as compact quartz, or possibly as an alkaline 

 silicate ; and, lastly, there would have been wanting the evidence 

 of the greater portion of the siliceous material having been, as it 

 were, continuously waylaid and absorbed, as it descended from the 

 surface of the ocean, into the colloidal protoplasmic mass resting upon 

 the immediate upper surface of the calcareous deposit. 



If we compare the evidence thus furnished of marked colloidal 

 action with what is known of the properties of silicic acid when 

 in the presence of another powerful colloid, and favoured by the 

 nature of the conditions as to unlimited time, low temperature, the 

 presence of various alkaline substances and finely comminuted 

 mineral matter, and the reign of almost perfect quiescence, I think 

 it will be admitted that, although many doubtful and obscure points 

 still remain to be elaborated, as a whole the view here advocated re- 

 ceives substantial confirmation in most of its leading particulars *. 



In conclusion, I beg to express a hope that, although the length 

 already attained by the present communication has debarred me 

 from bringing forward a number of important facts and observations 

 which would have materially strengthened my arguments, consider- 

 ing the complex nature of the inquiry and the special difficulties 

 belonging to it, the following conclusions have, on the whole, been 

 fairly sustained: — 1. That the silica of the flints is derived mainly 

 from the sponge-beds and sponge-fields which exist in immense pro- 

 fusion over the areas occupied by the Globigerine or calcareous 

 " ooze." 2. That the deep-sea sponges, with their environment of 

 protoplasmic matter, constitute by far the most important and essen- 

 tial factors in the production and stratification of the flints. 3. That, 

 whereas nearly the whole of the carbonate of lime, derived partly 

 from Foraminifera and other organisms that have lived and died at 

 the bottom, and partly from such as have subsided to the bottom 

 only after death, goes to build up the calcareous stratum, nearly the 

 whole of the silica, whether derived from the deep-sea sponges or 

 from surface Protozoa, goes to form the flints. 4. That the sponges 

 are the only really important contributors to the flint-formation 

 that live and die at the sea-bed. 5. That the flints are just as 

 much an organic product as the Chalk itself. 6. That the stratifi- 

 cation of the flint is the immediate result of all sessile Protozoan 

 life being confined to the superficial layer of the muddy deposits. 

 7. That the substance which received the name of '^ Baihyhius^^ 

 and was declared to be an independent living Moneron, is, in reality, 

 sponge-protoplasm. 8. That no valid litJiological distinction exists 

 between the Chalk and the calcareous mud of the Atlantic; and 



* See a paper, by the late Mr. Gl-raham, " On the Properties of Silicic Acid," 

 in the Proc. Roy. Soc. for June 1864, in which will be found a number of 

 interesting facts bearing upon the hypothesis put forward by me. I would 

 particularly du'ect attention to pp. 335-337. 



