QUARTZ AND FLINT 165 



itself may be built up of fibres of this mineral, a concep- 

 tion hardly in accord with its specific gravity. 



The subject is evidently still very obscure, and there is 

 need for renewed research, which, however, will make 

 great demands on the time, ingenuity, and skill of the 

 investigators.* 



* I take this opportunity to add the following' references on the 

 general subject : Buckland, Trans. Geol. Soc., vol. iv. p. 413. 

 Woodward, S. P., Geol. Mag., 1864, p. 145. Rupert Jones, Proc. 

 Geol. Assoc., 1878, vol. iv. p. 450. Sollas, W. J., Ann. and Mag. 

 Nat, Hist., 1881 (5), vol. vi. p. 384 and 437. Brit. Assoc. Rep., 1882, 

 p. 549 ; 1899, p. 744. Eenard and Element, Bull. ac. roy. Belgique, 

 1887 (3), vol. xiv. p. 773. Zirkel, Lehrb. Petrographie, 1894, vol. iii. 

 p. 549. 



