*RANSACTIONS OF SECTION C. 745 
Recently an author has attempted to overthrow the physico-chemical origin 
and replace it by a vital one. 
Some granules in certain so-called oolitic rocks have been shown to be of 
undoubted organic origin. As et, 
The present paper is an attempt to compare these granules with identical con- 
cretions the origin of which is known, and the formation of which can be observed 
in progress. 
The microscopic sections shown are a series from specimens kindly collected 
from the vicinity of Cheltenham by Mr. Gray, and for comparison are several sec- 
tions of somewhat similar structures, found at the present day, unquestionably 
inorganic, 
The true oolites and pisolites are seen to be concentric grains and masses of very 
variable dimensions in which three grades of crystallisation can be seen. 
In one, fragments of rock, shell, or other organic remains have been enveloped 
in crystalline calcite minutely saccharoidal in structure. 
In another similar nuclei have been enveloped in very distinctly marked con- 
centric bands of radiating needle-like or fibrous calcite. 
In a third, the enveloping material is finely granular, dirty, with the concentric 
bands very imperfectly marked. 
All these gradate into each other, and, what is more, alternate with each other 
in the same grain or pisolite. We have here nothing more than the varying con- 
ditions of slowness, turbidity, and movement of the water or other solution in which 
they were formed. 
Instudying oolites, the first question which arises is whether these structures were 
formed coincident with the deposit or as a secondary structure set up subsequently. 
The author thinks that the former is the true state of things. 
Accepting as granted that oolitic and pisolitic structures were coincident with 
the formation of the deposit in which we find them, the conditions necessary are 
nuclei, a solution of bicarbonate of lime, and gentle motion. 
In the first specimens shown was a section of a calcareous granule from the 
galleries of La Gardette mine near Bourg d’Oisans. The galleries have been 
abandoned for some years, and the calcareous water dropping from the roof has 
formed small pools in which granules of rock are churned up as each drop falls, and 
receives an infinitesimal coating of carbonate of lime, This process is a fairly rapid 
one, as the mine has not been abandoned for many years, and yet very thick crusts 
may often be found. Another specimen is from a gallery of quite modern date, 
cut into the side of Monte-Somma to catch the Olivella spring, and here we find 
the same rapid deposition of the concentric crystalline layers identical and often 
more perfect than in ordinary oolitic grains. The third and most striking examples 
are similar confetti from the mines of Laurium (Greece), where in small pools in 
the ancient galleries the most beautiful highly polished examples have been found. 
So far all of these are formed in very shallow pools of calcareous water, or 
have not even been immersed but only moistened by the liquid. The process is 
identical with the method adopted for depositing sugar from its solution in water 
in the manufacture of sugared almonds, ‘cannon balls,’ and other varieties of 
confetti, the only difference being the separation in the former case of the lime 
1 a of CO,; in the second, the evaporation in the rolling pans of the water 
ry heat, 
The formation of confetti when completely immersed occurs in the mineral 
water springs at the mud volcanoes of Paterno in Sicily. There, traversing 
fissures in a basalt, are springs of water supersaturated with OO, and a large 
quantity of bicarbonate of lime. These gush out with considerable violence, and 
keep in constant movement the grains of basalt or other solid loose fragments, as 
we frequently see in any spring. This supersaturated water reaches the surface 
under decreased pressure, much of the CO, escapes, and a deposit of CaCO, takes 
place on the walls of the fissure and on the grains that are being constantly 
churned up in the unstable solution. The specimens exhibited show examples of 
the great perfection of this concretionary structure, which is identical with that 
