While these discoveries may be considered as in progress, a Cornish gentleman, but one whose genius does honour to the nation, Mr. Robert Weare Fox, has deduced from galvanic action on metals, on their oxides, on their sulphurets, and on their saline solutions in water, the only theory that has yet accounted for the various phenomena observed in metallic lodes; and extending still further his investigations to the recently discovered connection
between electric energies and terrestrial magnetism, Mr. Fox has been enabled to give more than probable reasons for the extraordinary fact of some metals usually selecting, in all parts of the world, lodes or fissures running nearly east and west, and why other metals prefer rents at right angles to the former; and in respect to the fissures themselves, Mr. Fox has remarked appearances inducing him to believe that lodes of considerable breadth have not been formed by any one great and sudden rending of the earth; but that, in a manner similar to the rising or to the sinking of land, by the gradual action of causes now well known to exist, those clefts have been enlarged from time to time, and have as frequently received additional deposits, easily discriminated from each other.
Mr. Fox appears also to have settled beyond the possibility of doubt, the long-agitated question respecting the temperature of mines, by establishing a general relation between increases of heat and depth; although the ratio cannot be reduced to any definite formula, being liable to vary with the presence of more or less water, and with the different conducting power of rocks, since mines in granite and in killas differ by several degrees of heat at the same level: yet the increase corresponds so generally with greater descents into the earth, that elevation of temperature, and not the expense, nor the difficulty of exhausting water, appears likely to oppose the final limit to the progress of mines in depth.
In continuation of the same trains of reasoning
and of thought, Mr. Fox has been led to investigate the important elements of variation and dip of the magnetic needle; and in pursuing these inquiries, he has invented an instrument possessed of far greater accuracy than any one previously employed, and which at this moment is in actual use, through the enlightened liberality of our own and other governments, in various and distant portions of the globe.
Mr. Henwood is about to lay before the Public a Work containing the results of more extensive and scientific researches into the nature of Lodes and Fissures, than have perhaps been ever executed by any individual. Mr. Henwood is well known to geologists: I shall therefore only add what I think myself bound in duty to notice, that an original appointment in the Stanneries, and a subsequent promotion, have been bestowed on Mr. Henwood, through the medium of Her Majesty’s Duchy Officers, and principally of Sir George Harrison, in consideration of his scientific attainments, and of his desire to render these attainments available to the development of further inductions.
I have endeavoured to render the work cheap by adopting the octavo form, and by abstaining from all decoration, except a slight sketch of the Pitt Diamond, which by raising that family into an influential situation, has modified the fate of Europe in a degree impossible to have been contemplated
by the Regent Duke of Orleans, when he purchased that bauble at the expense of an hundred and thirty-five thousand pounds; and excepting also the Tomb of Archbishop Tregury, a view of Cotehele house, and the Seal of a Corporation, all of which had been previously cut on wood. I have abstained from further expense with the view of placing my work in the hands of as many persons in Cornwall as I possibly could, thereby diffusing the entertainment likely to arise from Local Anecdotes, from Provincial Occurrences, and from Historical Events, not of sufficient general importance for securing to themselves a place in national records. I have caused an ample Index to be prepared for the whole work; and among the Appendixes will be found an Index to the Survey of our most respected historian Mr. Carew; and I will add as a proof of my own disinterestedness, that I have engaged to leave with the Publishers all the profits, if any should arise, reserving to myself the much more probable alternative of sustaining the loss.
The concluding paragraph proves the least agreeable of my work. I am sorry to say, that the Typographical errors far exceed my expectation. I must entreat of all my readers to excuse them, and to correct the Text from the too extensive Tables of Errata. The want of early habit, dimness of sight, and absence from the Press, must be alleged on my behalf; perhaps the compositor may plead unusual names or terms, and subjects not rendered familiar by his ordinary practice.