' 
had been of but short continuance; for while it will be found that the 
smaller of these fragments are, to their very centres, converted into a 
crystalline mass, reflecting light from innumerable facettes, the larger exhibit 
the change only to a certain depth, the interior presenting itself as an 
impalpable calcareous basis, studded occasionally with joints of the encrinile — 
stems. 
488 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
More than once I have found a larger than ordinary 
joint, in part converted into cleavable calcite, which 
FAs flashed back reflected light ; while the greater part showed 
the structure of the fossil in no degree effaced. 
In the estimation of the temperature to which these 
erupted fragments had been heated, I operated upon the 
ordinary bituminous shales of the district ;—the imbedded 
shaly coke which is found in the tuff ;—and on the bombs 
of Lydian stone imbedded therein. | 
First, as regards the shales, that from the Kenly burn, the nearest point | 
where it crops out, yielded— 








S. G. Water. Gas. Carbon. Ash. 
L799 4°54 25" '29 or 27 60° 09 
That from Kinkell imbedded in the tufa— 
2°57 2° 64 6° °44 90 ° 92 
The gas from the latter is non-combustible, or almost so. The shale from | 
the tuff is grey-black,—very dark when the small amount of carbon is con- | 
sidered. | 
From the Kinkell shale, therefore, the greatest amount of the gas and | 
water has been distilled off, and the greatest amount of the carbon burnt | 
away. : 
It was next ascertained that the shales of the district parted with their gas | 
below a red heat; for antimony did not melt when inclosed along with them 
in the retort in which the distillation was conducted. 
In working downward, as regards temperature, in order to ascertain the | 
lowest point at which the change could be effected, the following process was 
adopted— | 
A flat block of iron, of some pounds in weight, had a dome-shaped cavity | 
turned out of one of its surfaces. On the surface of a large quantity of lead, 
which had been melted and cooled in an iron pot, a number of fragments of the 
bituminous shales were placed, and covered with the iron block, so as to be| 
