ON THE GOTHAM MARBLE 
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(a) The exact texture, polish, hardness and grain that 
characterize the Marble. 
(b) The uniformly finely crystalline structure. 
(c) The delicate banding. 
(d) The darkness of the thin bands, and paleness of the 
thicker ones, as a general rule. This is due in each case to 
the inclusion of a constant amount of pigment in a variable 
amount of precipitate. Abundant precipitation involves 
a thick, pale band, and vice versa. 
(e) But especially, the presence of typical “ hedge- 
structure.” (See fig. 5.) So marked is this that these 
stones are called “ Mulberry Calculi.” The “ hedge ” in 
both is dark coloured and concentrically ringed. The 
importance of this analogy is that we know that calculi are 
chemically formed. 
“ Hedge -structure ” is not peculiar to the Landscape 
Stone and calculi. It also occurs in “ fortification -agate, 
malachite, and stalactites. It is the hall-mark of a chemical 
origin. 
V. Modern Analogies. At the mouth of the Rhone, a 
crystalline calcareous deposit is found, due to evaporation 
of the lighter river water spread out on the surface. (See 
Geikie, Textbook of Geology, p. 453.) Carbonate of lime 
is only precipitated when -tl- of salt water have been 
evaporated (Bischof, Chemical Geology, I. p. 178). Near 
Nice, a hard varnish-like crust of carbonate of lime is 
deposited over rocks within reach of the sea, due to rapid 
evaporation. 
I have noticed on our own coasts, e.g. at Tintagel (in the 
Devonian slates), that in shallow rock pools a layer of 
hard . white calcareous deposit up to |-inch in thickness 
forms all over that area which is covered by water when the 
pool is nearly or quite full. The lustre, grain, and appear- 
ance strongly suggest Gotham Marble. It appears to be 
due to loss of carbon dioxide, owing to the heat of the sun, 
