36 
all instances the nucleus is covered with coatings of lime, or 
muddy deposit hardened into stone, but sometimes the Pisolite 
is made up of an aggregation of granules similar to those 
which compose the freestone, and some are merely small 
fragments of coral or limestone, worn into rounded grains. 
The coating of the nucleus was apparently a matter of time, 
as the Pisolites rarely show one coating only; on the contrary 
the better types show a succession of concentric rings, similar 
to those seen under a magnifier in the granules of the freestone 
the mode of formation was probably similar in both instances— 
the decay of rocks or coral reefs and the lime thrown down on 
the floor of the sea in the remains of minute organisms, which 
have contributed so largely to the formation of limestone 
rocks—or carried down to the sea by rivers and then precipi- 
tated, furnished the materials, and mechanical action led to the 
coating of the erratic fragments which compose the nuclei, 
and to the formation of the Pisolites. 
The Pisolites were probably derived from the north or 
north-east, as shown in the thickness of the deposit at Cleeve 
and Leckhampton hills compared with its thickness in the 
vicinity of Stroud; and it would seem, from the general 
resemblance in shape and size of the Pisolites, that their 
formation was regular and uniform. The period of their 
deposition was of considerable duration, as it appears that in 
some instances they were left uncovered by subsequent deposits 
long enough, according to Dr. Lycrrt, to admit of the growth 
of protozoa upon their surfaces. The passage of the fragments 
of shells, coral and other particles which compose the nuclei 
along a sea bottom covered with a muddy deposit, minute 
particles of which became attached to the moving fragments as 
they passed along, might perhaps account for the concretionary 
structure of the Pisolites. They might have then been heaped 
up in thick beds where the first deposit occurred, as shown in 
the sections at Cleeve, Leckhampton, Crickley and Birdlip, 
but were subsequently spread out beyond those points over a 
large area, gradually becoming thinner at Stroud, and at length 
ceasing altogether. 
CoE 
