58 THE DALES OF DERBYSHIRE. 
stalactite to the ascending stalagmite, a small portion of 
solid matter being deposited on each during the passage of 
every drop. These phenomena shew one of the properties 
of the material of which these dales are composed, which 
may help us in formulating our ideas on their formation, 
viz: that this material has the power of being dissolved, 
and afterwards being again deposited on slow exposure to 
the air. It is an interesting fact that the age of one of 
these peculiar formations existing in Poole’s Cavern has 
been estimated by an expert at thousands of years. 
Having thus far confined myself solely to the considera- 
tion of the broad features of some of the dales, I will try 
to lay before you (1) The nature of the material of which 
the grey rock, ever to the fore in the dales, is composed; 
(2) the means by which this material was accumulated; and 
(3) the forces by means of which it assumed its present 
shape. 
You will doubtless recall the limekilns at Ambergate 
Junction, and, probably, many others which abound in 
Derbyshire. 
The grey rock of which I have spoken so often, is a 
combination of lime and carbon dioxide gas. This gas 
which is more commonly known as carbonic acid gas is 
soluble to a considerable extent in water. 
Animals in breathing evolve carbon dioxide, and fuel of 
all kinds, containing carbon, behaves similarly on burning, 
in fact, carbon dioxide is given into the atmosphere from 
all kinds of life, decay and active combustion, and must 
have existed in large quantities in the cooling atmosphere 
of our planet. 
All rain water contains carbon dioxide in solution, and 
in this property which limestone posseses of dissolving in 
water, impregnated with carbon dioxide, we have the 
chief agent in the production of our Derbyshire Dales. 
To return to the later divisions of our subject. Where 
