THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



" per litora spargite museum. 



Naiades, et circilm vitreos considite fontes : 

 PoUice virgineo tencros hic carpite flores : 

 Floribus et pictum, divae, replete canistrura. 

 At vos, o NymphEB Craterides, ite sub undas ; 

 Ite, recurvato variata corallia trunco 

 Vellite muscosis e rupibus, et mihi conchas 

 Ferte, Deas pelagi, et pingui concliylia succo." 



N. Parthenii Giannettasii Eel. 



No. 123. JANUARY 1847. 



I. — On the Formation of the Flints of the Upper Chalk, 

 By J. TouLMiN Smith, Esq. 



[With a Plate.] 



Various theories have, at various times, been proposed to 

 explain the very curious and interesting phsenomena connected 

 with the presence of flints in the upper chalk. Having for some 

 time paid close attention to the facts, from which alone any true 

 theory can be framed, I would now offer a few observations on 

 some of the more prominent of those theories. 



The theories which have been proposed have had very differ- 

 ent objects, which it is desirable to distinguish clearly at the outset. 

 Thus, while Ehrenberg and Dr. Turner have suggested explana- 

 tions of the origin of flint itself, without entering into detailed 

 observations on the particular modes and forms in which we now 

 find it in the chalk, Dr. Buckland and Mr. Bowerbank have en- 

 deavoured to explain, not the origin of flint, but the forms and 

 modes in which it is now found. 



Disposed as I am to regard the explanation offered by Dr. 

 Turner*, combined with other sources known to exist, of the ori- 

 gin of the siliceous fluid as sufficient and satisfactory, the sug- 

 gestions of Ehrenberg being, at any rate, applicable in particular 



* See " Lecture on the Chemistry of Geology," Philosophical Magazine, 

 vol. iii. (183.3). 



Ann. ^ Mag, N. Hist. Vol. xix. 1 



