ly the edge of a similar sheet is exposed; and
every possible variety of shape and attitude between these two. He
will see also large spaces covered with little coloured dots, which
signify (as he will find at the margin) beds of volcanic ash. If he
look below the little coloured squares on the margin, he will see
figures marking the strike, or direction of the inclination of the
beds--inclined, vertical, horizontal, contorted; that the white lines
in the map signify faults, i.e. shifts in the strata; the gold lines,
lodes of metal--the latter of which I should advise him strongly, in
this district at least, not to meddle with: but to button up his
pockets, and to put into the fire, in wholesome fear of his own
weakness and ignorance, any puffs of mining companies which may be
sent him--as one or two have probably been sent him already.

Furnished with which keys to the map, let him begin to con it over,
sure that there is if not an order, still a grand meaning in all its
seeming confusion; and let him, if he be a courteous and grateful
person, return due thanks to Professor Ramsay for having found it all
out; not without wondering, as I have often wondered, how even
Professor Ramsay's acuteness and industry could find it all out.

When my reader has studied awhile the confusion--for it is a true
confusion--of the different beds, he will ask, or at least have a
right to ask, what known process of nature can have produced it? How
have these various volcanic rocks, which he sees marked as Felspathic
Traps, Quartz Porphyries, Greenstones, and so forth, got intermingled
with beds which he is told to believe are volcanic ashes, and those
again with fossil-bearing Silurian beds and Cambrian slates, which he
is told to believe were deposited under water? And his puzzle will
not be lessened when he is told that, in some cases, as in that of
the summit of Snowdon, these very volcanic ashes contain fossil
shells.

The best answer I can give is to ask him to use his imagination, or
his common sense; and to picture to himself what must go on in the
case of a submarine eruption, such as broke out off the coast of
Iceland in 1783 and 1830, off the Azores in 1811, and in our day in
more than one spot in the Pacific Ocean.

A main bore or vent--or more than one--opens itself between the
bottom of the sea and the nether fires. From each rushes an enormous
jet of high-pressure steam and other ga