172 
THE GEOLOGIST. 
foimd Orthk aud Euomphalus at Coorsan, but not Siji'ingopora. I conclude, 
therefore, tliougli not hastily, that these boulders may have belonged to some 
other exposed rock of Mountain-limestone further north. 
llomitain. Limestone. Coorson point (Lough Ree). Strike west and south, dip 
east. Crops out st the surface. Angle about 40 or 43 degrees. 
I have so named the "Productus" and " Spirifer" limestones on account of the 
abundance of the fossil mollusca of these two forms. The quarry at Coorsan 
Point, on the borders of Lough Ree, have yielded me about ten species, besides 
Terebratula and Euomphalus. Here the young geologist may work with pleasure 
and never tire ; and as he works hundi'cds of curious questions will arise and ask 
for solution. I stand on the summits of the quarry, with my back tov/ards the lake 
and see before me the huge rock in which the encrinite is barely a predominating 
featiu'c, but where thousands of Mollusca lie entombed. In some places there 
is a beautiful deposit of calcareous spar, fringed with metallic sulphide, marking 
the spot where there was a sudden extinction of life. There can be no mistake, 
for the molluscs are more numerous here than elsewhere.* How is this ? 
Yonder on the opposite side of the same lake, with a dip eastward, and a strike 
north and south — the same dip and strike remember, of the stratum before 
me — thousands of Encrinites lie buried with but comparatively few Molluscs. 
How can we account for this difference ? Ear away, at Bally keyron, with nearly 
the same strike and dip, another stone presents itself to the gaze of the geologist, 
black, bituminous, and shaly, almost destitute of fossils ; and, according to the 
lime-burners destitute of lime. These three quarries show at least three states 
of the Mountain-limestone seas ; how they were inhabited ; and how their 
inhabitants lived and died. It would be useless to speculate on the probable 
thickness of each bed. Reckoned by years how many must have intervened 
between the first and last deposit of animal-matter in those palaeozoic seas ! 
* la this quarry this fringing of metallic sulphate is very common. " It affords an inter- 
esting proof that animal matter in a state of putrefaction proves a powerful agent in the 
decomposition of mineral substances held in solution, and on their consequent precipitation. 
An earthen pitcher, containing several quarts of sulphate of iron, had been suffered to remain 
undisturbed and unexamined in a corner of Mr. Pepy's laboratory for about a twelvemonth. 
Some luckless mice had meanwhile fallen mto it and been di'owned ; and when it at lenth 
came to be examined, an oUy scum and a yellow siilphurous powder, mixed with hairs, were 
seen floating on the top, and the bones of the mice discovered lying at the bottom ; and it 
was found that over the decaying bodies the mineral components of the fluid had been 
separated and precipitated in a dark-coloured sediment, consisting of grains of pyrites and of 
sulphur, of copperas in its green and crj^staUine form, and of black oxide of iron. The ani- 
mal and mineral matters had mutuaUy acted upon one another ; and the metallic sulphate, 
deprived of its oxygen in the process, had thus cast do-svn its ingredients." — Hugh Miller's 
Old Red Sandstone," 7th ed., p. 247. Was it a solution of sulphate of iron cause* the 
sudden death of the moUusca in the Mountain Limestone seas ? 
