THE JURASSIC DEPOSITS WHICH UNDERLIE LONDON. TOL 
The vertical distribution of these fossils perfectly agrees with what 
has been made out by the study of the Gault in other localities, 
especially in the cliff-section at Folkestone. Microzoa were abundant 
in many of the beds, as was proved by washing them. But neither 
the evidence of the larger fossils, nor that of the microscopic forms, 
was sufficient to enable the geologist to define any of the numerous 
zones which have been established in the Gault series. It would 
appear, however, that while at Folkestone we have a thinner series 
owing to the fact that considerable periods were represented only by 
‘* Coprolite”’ beds, and in some cases possibly such layers indicate the 
denudation of strata already laid down, at Richmond the deposition 
of sediment, gradually changing in its characters, went on quite 
continuously from the beginning to the end of the Gault period. 
In the Gault at Richmond I was not able to detect any 
‘““junction-beds ” except the one at the base of the series. The 
upper portion of the formation exhibits clays of the marly com- 
position and pale colour so characteristic of the Upper Gault of 
Folkestone. A specimen of this Upper-Gault clay at Richmond 
taken from a depth of 1026 ft. from the surface, was found to con- 
tain nearly 33 per cent. of calcic carbonate, a result in tolerable 
accordance with that obtained by Mr. Hudleston in his analysis 
of the Upper Gault of Folkestone *. The lower portion of the Gault 
at Richmond has the dark blue colour, due to excess of pyrites, 
which almost everywhere distinguishes the lower beds of the Gault. 
In this part of the series numerous nodules of crystallized pyrites, 
and others composed of argillaceous ironstone, of a pale tint and 
usually of small size, abounded. Between the pale-coloured marly 
Upper Gault and the dark-coloured pyritous Lower Gault there 
appears to be at Richmond the most perfect and insensible grada- 
tion. 
The lowest bed of the Gault becomes very sandy and is filled with 
dark-green grains of glauconite. This sandy bed passes down into 
the well-known junction-bed, containing many perfectly rounded 
grains of white quartz, a considerable quantity of similar grains of 
red jasper, and many subangular fragments of quartzite, crystalline 
limestone, and other hard rocks, some of considerable size. Inter- 
mingled with these we find a few nodules of pyrites and many of 
phosphate of lime, the latter being sometimes dark coloured and 
apparently rounded and waterworn, and at others lighter in colour 
and irregular in form. A specimen of these phosphatic nodules 
was kindly analyzed for me by Dr. Percy F. Frankland, F.I.C., in 
the Laboratory of Agricultural Chemistry, attached to the Science 
Schools at South Kensington. The percentage of phosphoric anhy- 
dride was found to be 20-21. 
One of the cores brought up from the well at a depth of 1141 ft. 
6 in. exhibits the actual junction of. this phosphatic bed with the 
rocks below. 
* Quart. Journ. Geol. Soc. vol. xxx. (1874), p. 354, 
