THE society's NOTE-BOOKS. 241 



Flint. — The formation of Flint nodules is a puzzle which has 

 frequently occupied my thoughts without satisfactory conclusion. 

 I am inclined to favour the chemical theory, with the silica playing 

 the part of an acid and existing thus in combination in the ocean 

 — say, as silicate of lime or other salt, resting upon the chalk 

 bottom. Imagine that for some reason a fresh body comes into 

 play. The Hme leaves the flint for this new body, for which it has 

 a greater affinity, and the silica is set free in a fluid condition ; 

 that it sinks to the bottom of the ocean, enveloping in the way 

 sponge and such-like organisms as it may meet, more or less 

 insinuating itself among the chalk, thus acquiring its often gro- 

 tesque forms, and, gradually hardening, receiving at the same time 

 during the process a coating of silicate of lime, such as we see on 

 our flint nodules, be they large or small. We must think of all 

 this done on the grand scale upon which Nature works, and that 

 after this the formation of chalk was continued. No doubt, the 

 chalk was in a semi-fluid condition. 



Flint must be one of the most extensively diflused bodies in 

 nature. No doubt, water dissolves some portion, but it must be 

 in almost all soils in different combinations. The delicate root- 

 fibres of plants which require the presence of flint must exercise 

 their wondrous powers of selection, and carry up the flint in solu- 

 tion to deposit it on the surface to give strength to the plant, as in 

 the wheat and others, to enable the otherwise weak stem to 

 support a heavy head of corn. The canes of tropical countries 

 consist to a large extent of this material, not only in their highly- 

 polished exterior, but also in the interior structure, where it pre- 

 sents longitudinal formations more resembling the familiar spicules 

 of sponge. 



It is easy to image more or less fluid sihca in its passage 

 to the bottom enveloping small organisms, carrying them with it, 

 hardening them, and presenting them in the state in which we 

 observe them. Nevertheless, many questions, even in theory, are 

 unsolved in regard to flint, and the slide referred to above by Mr. 

 Nicholson is a case in point. I apprehend that when the flint in 

 this case overflowed the chalk, which it enclosed, the chalk was 

 in a more or less moist state, the water containing silica in some 

 form in sohition. This affords much subject for thought. 



W. Case. 



Volvox globator. — Having had the good fortune to meet with 

 a great number of these beautiful objects in a pond near here 

 (Stroud, Gloucestershire), I have been experimenting to ascertain 

 what is the best medium to preserve them in, and have met with 



