164 Dr. Wallich on the Origin of the 



racteristic forms assumed by the flint nodules that may not 

 be found in every geological textbook ; and upon the most 

 difficult and puzzling question of all (namely, the cause of 

 the stratification of the flints), although he shows that he 

 regards it as part and parcel of the Flint question, by just once 

 (at p. 441) confessing it presents " a difficulty," from first 

 to last he remains significantly silent. 



I may observe, in reference to the last- mentioned fact, that 

 I should have been content to discuss Mr, Sollas's theory of 

 the formation of flint so far as it goes, and to leave entirely 

 out of sight those points on which it would appear that he has 

 been unable to arrive at any conclusion whatever, had he not 

 indulged in such unjustifiable observations as the following : — • 

 " The last question which remains for discussion is the origin 

 of tlie various external forms assumed by flint. A good deal 

 of misconception appears to have arisen on the subject through 

 a too exclusive attention to one particular form of flint arbi- 

 trarily selected as a type of all others. For this (generally the 

 irregular nodular form) a theory is framed which is then made 

 to account for the rest. Thus, when Dr. Bowerbank attempted 

 to show that flints are silicified horny sponges, he accounted 

 for the flint-veins of the chalk by supposing them to be 

 horny sponges which had grown over the sides of an open 

 fissure at the cretaceous sea-bottom ; and Dr. Wallich, after 

 giving an explanation of flint nodules and layers, speaks 

 of the veins as formed by a ' sluggish overflow ' of silica- 

 saturated protoplasm ' into fissures in the chalk.' There does 

 not appear much to choose between these rival explanations of 

 the veins ; both are attempts to square a preconceived hypo- 

 thesis with an obnoxious fact ^^ {loc.cit. p. 450). 



Mr. Sollas is doubtless aware that Dr. Bowerbank can no 

 longer answer for himself. He has, however, associated my 

 name with that of a universally respected and known scientific 

 thinker and writer, whose researches on the Sponges alone 

 ought to have protected him from an imputation which, applied 

 as it has been to myself as well as to Dr. Bowerbank, I can 

 only describe as being wholly unfounded. 



Mr. Sollas has taken care not to state at what page the 

 words he here quotes from my paper are to be found. I will 

 supply the omission. The seven words in question consti- 

 tute the sole allusion to the flint-veins made by me, from 

 beginning to end of my paper. The context, now furnished, 

 will show that the formation of the veins was not what I was 

 speaking about, but the " homogeneousness " of the colloid 

 material contained in the fissures. In my paper I ofiered no 



