A. J. Jukes-Browne—Relative Age of Fiints. 315 
V.—Tue Revative AGE or FLin Ts. 
By A. J. Jukes Browne, F.G.S. 
AY R. G. ABBOTT is quite right in saying (Guo. Mac. for June, 
p- 275) that much work has yet to be done before we under- 
stand the formation of flints, and I would add that the work required 
must include observations on other siliceous concretions such as 
chert and cherty nodules of all kinds. It is also unquestionably 
‘important that we should, if possible, ascertain whether such con- 
cretions were formed contemporaneously with the deposits in which 
they are now found, or whether they are a sort of separation product 
formed during the consolidation of the rock after upheaval above 
the sea. 
To Mr. Abbott, as to many observers, the vertical veins of flint 
so often present in Upper Chalk, and termed by him “tabular flint,” 
prove a stumbling-block. These veins do certainly appear to have 
been formed during or after the consolidation of the Chalk; but 
need we on this account proceed to assume that all other flints and 
cherts are of subsequent growth? Surely it is at least possible that 
some forms of flint are of contemporaneous origin, while others may 
be of subsequent date. 
- Before discussing this difficult question let us clear the ground a 
little by making a rough classification of flints. Mr. Abbott makes 
no mention of the horizontal or interbedded floors of flint which are 
sometimes continuous over many square miles (e.g. in Kent and 
Lincolnshire). These are much more correctly called “tabular flints ” 
than the vein-courses which cut the beds at various oblique angles. 
No one who examines them could doubt that they are interstratified 
beds and not infilled cracks, though of course it is open to question 
whether they were always layers of flint. 
Chalk flints may I think be classed under four heads :— 
1. Nodular flints. 
2. Tabular flints and flint floors. 
3. Vein-courses. 
4, Paramoudras. 
An acquaintance with flints and their different modes of occurrence 
extending now over more than twenty years has only served to 
strengthen my belief that flint nodules and tabular flint-floors 
have been formed while the Chalk was being accumulated. I would 
not deny that the making of a flint may have been a long and slow 
process; there may have been a succession of phases and changes 
before an incipient nodule became a hard and glassy flint, but I think 
that the whole process must have been accomplished while the 
superincumbent chalk was still soft chalky ooze, and while it was 
still saturated with sea-water. 
It is, perhaps, not generally known that the flints of the successive 
zones of the Upper Chalk have special characters of their own. 
The characters of the flints in a given zone are not exactly the same 
throughout England, but within certain areas they appear to be 
constant, and they have been used by Dr. Ch. Barrois and the late 
