of those who judge not for themselves in forming their notions, but look up to men of science for authority.  Such is the case with some part of the Theory of the Earth, which I have given, and which will probably give offence to naturalists who have espoused an opposite opinion.  In order, then, to obtain the approbation of the public, it may not be enough to give a theory that should be true, or altogether unexceptionable it may be necessary to defend every point that shall be thought exceptionable by other theorists, and to show the fallacy of every learned objection that may be made against it.  It is thus, in general, that truth and error are forced to struggle together, in the progress of science; and it is only in proportion as science removes erroneous conceptions, which are necessarily in the constitution of human knowledge, that truth will find itself established in natural philosophy.

Mr Kirwan has written a dissertation, entitled, Examination of the Supposed Igneous Origin of Stony Substances, which was read in the Royal Irish Academy.  The object of that dissertation is to state certain objections, which have occurred to him, against the Theory of the Earth published in the Transactions of the Edinburgh Royal Society; and he has attacked that theory in all the points where it appears to him to be vulnerable.  It is to these objections that I am now to give an answer.  The authority given to this dissertation, by the Royal Irish Academy, as well as the reputation of the author, make it necessary for me to endeavour to put in their true light the facts alleged in that performance, and to analyse the arguments employed, in order to judge of the reasoning by which the theory of mineral fusion is refuted in this Examination.

A theory founded on truth, and formed according to the proper rules of science, can ever suffer from a strict examination, by which it would be but the more and more confirmed.  But, where causes are to be traced through a chain of various complicated effects, an examination not properly conducted upon accurate analytical principles, instead of giving light upon a subject in which there had been obscurity and doubt, may only serve to perplex the understanding, and bring confusion into a subject which was before sufficiently distinct.  To redress that evil, then, must require more labour and some address; and this is an inconveniency that may be looked for, more or less, in every controversial discussion.

I do not mean to enter any farther into the defence of my theory in this chapter, than what is necessary to answer a man of science and respectability, who has stated his objections.  The observations which he has made appear to me to be founded on nothing more than common prejudice, and misconceived notions of the subject.  I am therefore to point out that erroneous train of reasoning, into which a hasty superficial view of things, perhaps, has led the patron of an opposite opinion to see my theory in an unfavourable light.