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Updated: May 24, 2025
"You know Enriquez's sanguine temperament. Perhaps he is already given to evolving theories without a sufficient basis of fact. Still, he has the daring of a discoverer. His ideas of the oolitic formation are not without originality, and Professor Dobbs says that in his conception of the Silurian beach there are gleams that are distinctly precious." I looked at Mrs.
The immense areas in some parts of the world, for instance in South America, of bare metamorphic rocks, which must have been heated under great pressure, have always seemed to me to require some special explanation; and we may perhaps believe that we see in these large areas, the many formations long anterior to the silurian epoch in a completely metamorphosed condition.
THE APPALACHIAN REGION. Where the Silurian system is most fully developed, from New York southward along the Appalachian Mountains, it comprises four series: 4 Salina . . . shales, impure limestones, gypsum, salt 3 Niagara . . . chiefly limestones 2 Clinton . . . sandstones, shales, with some limestones 1 Medina . . . conglomerates, sandstones
It is marked by the rapid extension of the fishes; for, although the fishes began in the uppermost Silurian, they first became abundant in this time. These, the first strong-jawed tyrants of the sea, came all at once, like a rush of the old Norman pirates into the peaceful seas of Great Britain. They made a lively time among the sluggish beings of that olden sea.
But they are also met with in some part or other of the world at the junction of almost all the other principal formations, and sometimes the subordinate divisions of any one of the leading groups may be found lying unconformably on another subordinate member of the same the Upper, for example, on the Lower Silurian, or the superior division of the Old Red Sandstone on a lower member of the same, and so forth.
Cassian beds exhibiting an abundant fauna of mixed mesozoic and palæozoic types, in rocks of an epoch once supposed to be eminently poor in life; witness, lastly, the incessant disputes as to whether a given stratum shall be reckoned devonian or carboniferous, silurian or devonian, cambrian or silurian.
But let us compare a given extent of Silurian or Devonian sea-shore with an equal extent of sea-shore belonging to our own time, and we shall soon be convinced that the one is as populous as the other. On the New-England coast there are about one hundred and fifty different kinds of fishes, in the Gulf of Mexico two hundred and fifty, in the Red Sea about the same.
Around the flanks of Muilrea, beds of purple quartz-felstone with tuff are interstratified with the Upper Silurian grits and slates. Lower Silurian Period. Volcanic action was developed on a grand scale during the Arenig and Caradoc-Bala stages, both in Wales and the Lake district, and in the Llandeilo stage in the South of Scotland.
Consequently, if my theory be true, it is indisputable that before the lowest Silurian stratum was deposited, long periods elapsed, as long as, or probably far longer than, the whole interval from the Silurian age to the present day; and that during these vast, yet quite unknown, periods of time, the world swarmed with living creatures.
And it is remarkable that the Silurian fishes are here only represented in genera; the whole of the SPECIES of that era had already passed away.
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