Burton: The Cleveland Ironstone. 167 
Of course these experiments were made under conditions 
which were intended to produce results in a lifetime and cannot 
be compared with the weak solutions and unlimited time 
with which nature works, but the results obtained support the 
suggestion that the replacement action in the ironstone beds 
may not have entirely ceased, although we are unable to detect 
the means by which it may still be carried on. 
The chemical side of the question has been so fully dealt 
with by others that it is unnecessary to go further into it now. 
If, however, it is clear that the conversion of limestone into 
ironstone is possible, there is still to be considered the source of 
the iron which has replaced the lime. 
Iron is one of the most universally diffused substances in 
the composition of the crust of the earth, and during the enor- 
mous period of time which has elapsed since the envelope 
round the unknown condition of the interior became solid 
matter, many and often repeated cycles of chemical change 
must have taken place. Iron has been segregated and again 
diffused under the changing conditions which have taken place. 
The New Red Sandstone, for instance, has taken up a thin 
pellicle of iron as a covering to the grains of sand of which 
it is composed. Springs have in their wanderings through the 
interior taken up from the rocks and soil large quantities of 
iron in solution, and left it as a solid deposit in streams and 
lakes. Earth movements have produced faults and cracks 
and fissures, and by friction have generated great heat; and 
mineral veins and iron bearing lodes have resulted. Lavas 
from volcanoes and dykes have spread over, in, and under the 
surface, and these contain vast quantities of iron. 
From sources of this character all the iron necessary for 
the Cleveland beds might have been obtained. 
It seems probable also that the physical conditions in later 
liassic times were such as would permit us to contemplate the 
derivation of the iron from these sources. 
On the sections and the map on which I have drawn the 
lines of the sections, it will be seen that at Eston the main seam 
is the thickest, and that as we proceed east and south, clay 
shales and ferruginous shales take the place of the ironstone ; 
and if the section had been continued south and south-east as 
far as the beds are recognisable, to say, beyond Thirsk, the same 
thinning of the seams and replacement by shales would be 
seen. These records of the material carried down by Liassic 
streams indicate very clearly that when the Eston main seam 
was under water the shore line of the ancient sea was not very 
far distant and that there must have been streams carrying 
out the finely divided wreckage of land areas, east and south, 
in suspension. 
It is generally admitted that the area of the Penines north 
1913 April 1 
