75 
ON FIRE CLAYS. BY C. W. BINGLEY, ESQ., PH. D., F.C.S., OF 
WHITLEY HALL, NEAR SHEFFIELD. 
Amongst the various clay deposits in the kingdom, there 
are none of equally deserving importance to this town 
as those which occur in the coal formation, and are known 
as fire-clays. Of these there are fortunately several very 
considerable ones in the neighbourhood of Sheffield, skirting 
the border of the coal formation and the millstone grit of 
the high moors. To these my attention has been more 
particularly directed than to those obtained from other 
deposits in the same formation. As all seem to possess one 
property in common, that of making fire-bricks, yet, as is 
well known to the manufacturers who require fire-bricks in 
the construction of their furnaces and fire-clays for crucibles, 
a very considerable difference exists amongst them as regards 
their qualification to resist heat and withstand any sudden 
change of temperature when intensely heated, as in the case 
of the withdrawal of crucibles, containing metal in a high 
state of fusion, and in the cooling of furnaces. "With the 
object in view of accounting for this difference of quality, 
I commenced some time ago a course of experiments on 
several of them, intending as any opportunity might occur 
to continue them until I had completed my researches, so 
far as to comprise all the various deposits of the neighbour- 
hood. So far I have examined rather more than a dozen, 
and from these I shall select a few for reference to on this 
occasion, premising that I must nevertheless request your 
indulgence for any incompleteness in the present instance 
attendant upon my having only had a few days' notice to 
collect my notes of the experiments, so as to condense them 
into the form of a report. Commencing with an analysis of 
each, I do not intend to particularise the source or precise 
locality of each individual specimen selected, inasmuch as it 
