164 Burton: The Cleveland. Ironstone. 
To which of the three do the Cleveland beds belong ? 
The thin bands in some places; the ever constant evidence 
of a changing littoral in some parts of the area; the strong 
suggestion of estuarine conditions here and there, and the 
probability that shallow water prevailed where the seams 
are thickest, prove to my mind that the beds are not directly 
organic. Microscopic examination reveals nothing more than 
a comminuted fragment of a shell, perhaps as the nucleus of 
an Oolitic grain, and I am strongly of opinion that the beds 
were formed out of the debris of pre-existing limestone forma- 
tions. The mixture of impurities of silica and alumina 
strengthens this view. The Permian, Triassic and Liassic period 
was one of great earth movements, and the older rocks to the 
west were being elevated and fractured. It is probable, if 
not certain, that much disturbance of a volcanic nature was in 
progress to the north-west, giving exactly those alternating 
conditions of stability and instability required ‘for the rapid 
wearing down of pre-existing rocks, including Permian and 
Carboniferous formations, which are necessary for the building 
up of the Lias, and the ironstone series in particular. Mr. 
Stead, in his usual thorough manner, has investigated this sub- 
ject, and has given the results in a paper read before the 
Cleveland Institute of Engineers in February, 1910, where 
he says he believes he found the original substance imprisoned 
in the vertebral column of a Plesiosaurus propinguus, occupying 
what was originally the spinal cord. It consisted of Oolitic 
mineral closely resembling the ironstone itself in every par- 
ticular. The bone surrounding it was very dense, and it 
appeared to be possible that the substance inside, being 
surrounded by a dense non-porous envelope, might have 
been protected from the influence of percolating solutions, 
and would perhaps approximate in composition and character 
to the original deposit. 
He gives the analyses of both the.fossil bone and the 1m- 
prisoned substance ; that of the latter is :— 
Ferrous carbonate res i: 15.58% dried at 212° F. 
Iron Pyrites i 2 0.82 
Alumina A “i ae 7.00 
Silica x X i te 19.80 
Calcium carbonate nh De 51.16 
Calcium Phosphate.. ia 253 
Magnesia a .% Ag 1.67 
Organic matter, etc. Ts 1.44 
100.00 
The lithological character of the substance under the micro- 
scope closely resembles that of the Ironstone. 
Naturalist, 
