153 MR. F. D. LONGE ON THE FORMATION OF FEINTS JN CHALK. 
Whatever this mysterious force may be, it would appear to be 
acting in the same manner under different conditions in producing 
amorphous or spherical mineral concretions, as in the production of 
crystalline forms. 
Sections of flint nodules often show bands of different colours 
or different shades of colours, particularly in their outer edges, 
which would seem to imply that the flint grew by the accretion of 
separate laminse of material somewhat differently constituted, as 
to the other ingredients mixed with the silica, as, for instance, the 
proportion of oxide of iron contained. Indistinct lamination is 
also to be seen in the granular coating of some flints. This feature 
would seem to identify the formative process of flint with that of 
the agate, and of the spherical concretions which occur in both 
clays and limestones. 
The tendency to form globular masses is a noticeable feature in 
the class of mineral concretions to which flint belongs, as distin- 
guished from the prismatic and rectilinear forms assumed by 
crystals ; though I believe many minerals — flint is not one — are 
found in nature both as prismatic crystals and as amorphous 
concretions. 
The round flint concretions of our chalk pits are, in a few 
cases, the pebbles of our gravel pits, and sea beaches, which are 
generally very little altered in form or appearance since they were 
separated from their chalk matrix, in some not very distant 
geological period. 
The conditions under which the flint grows and has grown in 
the chalk, precludes its being formed in regular spheres. But the 
spherical laminations so often manifested, and the rounded form of 
the nodules, show that they are formed under the action of the 
same forces which produce the more pei'fect spheres in chemical 
preparations. The young flint may maintain a more or less 
spherical iorm, but as it grows larger it has to adapt its form to the 
conditions under which it is supplied with material, or under 
which it can project itself into the solid chalk. Hence the curious 
tubercular forms assumed by the larger flints. 
The spheroidal growth, and lamination of flints, show that they 
are not formed by the mere deposition of material under the action 
of gravitation, as in the case of tabular bands of chalk or other 
limestone. Gravity may play part in the supply of material, but 
