88 



THE GEOLOGIST. 



owing to the abundant remains of Avicula cygnipes in it. Towards 

 the east the "Pecten seam" acquires more the concretionary spheroidal 

 form, as usual with argillaceous deposits, and approaches nearer in 

 appearance to the hard, compact clay-stones of the coal-measures at 

 Bierley and Low Moor. As the diminution in thickness towards the 

 south-east and west from Eston is very gradual, it is impossible to 

 fix any line of demarcation to point out the exact boundary within 

 which it is of sufficient value to be worked. 



An interesting paper was read by Mr. H. C. Sorby, E.Gr.S., before 

 the West Riding Geological and Polytechnic Society,* in which the 

 writer endeavoured to show that the Cleveland ironstone was altogether 

 an altered limestone-rock, in which the carbonate of lime had been 

 changed to carbonate of iron, by the percolation, probably, of some 

 chalybeate water, and that the ironstone was not deposited in its present 

 condition. I confess that I am not inclined to adopt those views 

 without further examination, as I think the whole analysis of the ore 

 does anything but favour such a theory. In concluding my notice of 

 this most important division, I need only add that these Lias bands are 

 very extensively wrought, at Eston, Upleatham, Codhill, Hutton 

 Lowcross, Belmont Banks, Rosedalef on the coast, Grosmont in 

 Eskdale, and several other parts of Cleveland. The usual royalty- 

 rent paid in the district varies from fourpence halfpenny to eight- 

 pence per ton of twenty -two and a half hundred weight ; and, so 

 cheaply may it be worked, that it can be sold with profit at half-a- 

 crown a ton at the mine's mouth. Such brief statistics may be of 

 interest to those readers who are in any way connected with this 

 great branch of manufacture. I now ascend to 



d, The Upper Lias Shales, which also possess great importance in 

 an economic point of view. After about thirty to forty feet of hard 

 sandy shale, which is the lowest rock in the upper Lias, we find what 

 is generally called the " Hard Jet Rock," a variable shale twenty feet 

 in thickness, enclosing irregularly jet and pyrites. On the coast, as 

 at Kettleness, the rock is harder and more productive of jet than in 

 the interior of the country : the raw material is, according to quality, 

 worth from two shillings to twelve shillings per pound, and the total 

 value of the jet-manufacture at Whitby, whither it all goes from this 

 district, is estimated at twenty thousand pounds per annum. Owing 

 to the great quantity of non-pyrites, or nodules of sulphuret of iron, 

 which these shales contain, it not unfrequently happens that upon 

 being dug out in the search for jet, and exposed to the action of 

 moisture and the atmosphere, the sulphur combines with the oxygen 

 of the air and of the water, and in this decomposition sufficient heat 

 is generated to cause spontaneous ignition. An instance of this 

 decomposition occurred not long ago in Westerdale, and caused no 

 little wonder amongst the homely inhabitants ; it is, however, of 



* Report of Society's Proceedings, 1S56-7, p. 457. 



t There are two " Kosedales" in this district celebrated for their ironstones : 

 one near Staith on the coast, and the other fifteen miles inland. 



