proves their importance, and even necessity. The facts which are the basis of geological reasonings can be known to the majority even of well-educated persons, only by testimony; as, in the greater number of instances, they are to the author himself. To bring forwards, therefore, the statements of the most competent authorities, in their own words, is due to the right position of the subject and to the satisfaction of the reader. Should it be objected, that some of those citations contain reasonings and opinions, besides statements of fact; the reply is, that they are the reasonings and opinions of men who thoroughly understood the grounds upon which they are built; and that, therefore, the inferences which such men have seen to be just, are entitled to stand in the next line of authority to their testimony as eye-witnesses and labourers in the great field. It involves no disrespect to the multitude of pious and intelligent persons, to say that they cannot form an independent opinion upon many subjects in Natural Philosophy. It is no dishonour to accept the conclusions of NEWTON and his followers, though we confess ourselves unable to read the Principia.

FOURTH EDITION.

As the requirement for the publication of these Lectures arose from their having been delivered to an audience, at the Congregational Library, I have not thought myself at liberty to add or omit or change any part, paragraph, or sentence, except in some two or three instances, not considerable, and of which in the passages an intimation is given. But in the Appended Notes, I have felt no restraint. They have been increased in each of the subsequent editions, with the view of placing my readers, as much as is for me possible, in the advancing positions of geological knowledge. The amount of this accumulation is now not small: for I have felt it my duty to verify the encomium with which, on the publication of the third edition, I was honoured by the REV. DR. WHEWELL, the Master of Trinity College, Cambridge. He then wrote these words: "I perceive you have given it the interest which belonged to the former editions, of making your readers acquainted with the

most recent geological discussions.

On this account,

it cannot fail to be a general favourite."

Of those Notes peculiar to this edition, I have to regret the not having, in due time, adopted a uniform mode of designation. Some of them have a date, or imply a reference to time; others are included in brackets; and to others, the words Fourth Edition are prefixed.

I should feel it not becoming to relate the expressions of approbation with which this book has been favoured by eminent men of science, in our own country and in the North American States; or, what is a more exalted gratification, the testimonies of usefulness in relation to its religious element. But it would be a failing to the great cause for which I plead, if I did not avail myself of a communication which, to well-informed persons, will have the appropriate interest in a very high degree. It is a part of a letter with which SIR JOHN HERSCHEL honoured me in the summer of 1843.

Abstractedly, one might have thought that such wild and vehement denunciations' as those you cite from * * and others, were hardly worth very seriously handling. Yet, in effect, I am disposed to regard it as doing good service, not only to science but to religion and moral feeling, to put down, as you have done, with a strong (though not a cruel) hand, that sort of barking and yelping. There cannot be two truths

in contradiction to one another: and a man must have a mind fitted neither for scientific nor for religious truth, whose religion can be disturbed by geology, or whose geology can be distorted from its character of an inductive science, by a determination to accommodate its results to preconceived interpretations of the Mosaic cosmogony.

"I should hope that, on this painful and troublesome point, your work will prove final, and put an end, once and for ever, to the sort of outcry in question; or at least so far crush it, that this and the next generation may be allowed to pursue their geological researches in peace.

It is my duty to add that these citations from private letters are thus made public, with the kind assent of the writers.

HOMERTON COLLEGE,

February 5, 1848.

J. P. S.