the
porcellanite formation of Trinidad, curious to geologists, which
reappears at several points in Erin, Trois, and Cedros, in the
extreme south-western horn of the island.

How was it formed, and when? That it was formed by the action of
fire, any child would agree who had ever seen a brick-kiln. It is
simply clay and sand baked, and often almost vitrified into
porcelain-jasper. The stratification is gone; the porcellanite has
run together into irregular masses, or fallen into them by the
burning away of strata beneath; and the cracks in it are often lined
with bubbled slag.

But whence carne the fire? We must be wary about calling in the
Deus e machina of a volcano. There is no volcanic rock in the
neighbourhood, nor anywhere in the island; and the porcellanite,
says Mr. Wall, 'is identically the same with the substances produced
immediately above or below seams of coal, which have taken fire, and
burnt for a length of time.' There is lignite and other coaly
matter enough in the rocks to have burnt like coal, if it had once
been ignited; and the cause of ignition may be, as Mr. Wall
suggests, the decomposition of pyrites, of which also there is
enough around. That the heat did not come from below, as volcanic
heat would have done, is proved by the fact that the lignite beds
underneath the porcellanite are unburnt. We found asphalt under the
porcellanite. We found even one bit of red porcellanite with
unburnt asphalt included in it.

May not this strange formation of natural brick and china-ware be of
immense age--humanly, not geologically, speaking? May it not be far
older than the Pitch Lake above--older, possibly, than the formation
of any asphalt at all? And may not the asphalt mingled with it have
been squeezed into it and round it, as it is being squeezed into and
through the unburnt strata at so many points in Guapo, La Brea,
Oropuche, and San Fernando? At least, so it seemed to us, as we sat
on the shore, waiting for the boat to take us round to La Brea, and
drank in dreamily with our eyes the beauty of that strange lonely
place. The only living things, save ourselves, which were visible
were a few pelicans sleeping on a skerry, and a shoal of dolphins
rolling silently in threes--husband, wife, and little child--as they
fished their way along the tide mark between the yellow water and
the green. The sky blazed overhead, the sea below; the red rocks
and gr