field.

And in the last forty years--since that great and sound idea has
become rooted in the minds of students, and especially of English
students, geology has thriven and developed, perhaps more than any
other science; and has led men on to discoveries far more really
astonishing and awful than all fancied convulsions and cataclysms.

I have planned this series of papers, therefore, on Sir Charles
Lyell's method. I have begun by trying to teach a little about the
part of the earth's crust which lies nearest us, which we see most
often; namely, the soil; intending, if my readers do me the honour to
read the papers which follow, to lead them downward, as it were, into
the earth; deeper and deeper in each paper, to rocks and minerals
which are probably less known to them than the soil in the fields.
Thus you will find I shall lead you, or try to lead you on,
throughout the series, from the known to the unknown, and show you
how to explain the latter by the former. Sir Charles Lyell has, I
see, in the new edition of his "Student's Elements of Geology," begun
his book with the uppermost, that is, newest, strata, or layers; and
has gone regularly downwards in the course of the book to the lowest
or earliest strata; and I shall follow his plan.

I must ask you meanwhile to remember one law or rule, which seems to
me founded on common sense; namely, that the uppermost strata are
really almost always the newest; that when two or more layers,
whether of rock or earth--or indeed two stones in the street, or two
sheets on a bed, or two books on a table--any two or more lifeless
things, in fact, lie one on the other, then the lower one was most
probably put there first, and the upper one laid down on the lower.