CHAPTER V. ON THE MULTIPLICATION OF WOOD-CUTS. Design on wood-cuts, 270. Process for multiplying wod cuts, 271. Conclusion, 272. CHAPTER VI. ON MULTIPLICATION OF THE DAGUERREOTYPE. Value of the electrotype for the Daguerreotype, 273.-Process for obtaining the duplicate, 274. BOOK THE SIXTH. ON GALVANIC ETCHING, Action on the positive pole, 275. Etching by nitric acid, 276. Faults in the biting, 277. Galvanic etching, 278. vantages of galvanic etching, 280. Remarks, 282. Accelerating circumstances, 279. Ad- CONCLUSION. PREFACE. LAST summer I was requested to write an epitome of the electrotype, a task which I was most unwilling to undertake. Upon being much pressed, however, I at length consented, solely on account of my conviction of the necessity which then existed of investigating the subject experimentally. I accordingly entered upon my task, and as soon as I had satisfactorily developed the laws regulating the precipitation of the metals, I found that the isolated fact of the reduction of copper, was but one of an extensive series of facts, all of which were regulated by the same laws; and instead, therefore, of having before me, simply the electrotype, as the boundary of my labours, I found myself embarked upon a new and comprehensive science. The laws above mentioned led to the various new applications which are interspersed throughout this volume. Many of them I had originally thought of patenting, but upon second consideration I determined to throw the laws and principles open for the benefit of the arts and manufactures of our great country. The application of these laws and principles are fully detailed, and if they tend to further that great object, it will indeed be an ample recompense for all my labours. Every thing that is new in this treatise is given freely to the manufacturers of this country, and I may mention that every thing which I have hitherto invented or improved upon, has also been in a like manner thrown open. The scientific man in England has neither to expect remuneration from an Emperor, as the Russians have, nor from the Chamber of Deputies as the French have, nor can he look forward to those honors and distinctions which are conferred upon illustrious Germans. For what then does he labour? It is solely for the sake of science, and he is contented and satisfied with developing new scientific truths, or promoting the prosperity of our national manufactures. The plan upon which this work is arranged, is that which I considered would prove most serviceable to the practical man. A brief epitome of galvanism is here subjoined, because the science of electro-metallurgy is radically founded upon that principle, that principle, and therefore absolutely dependent upon a thorough knowledge of it, for its successful practice. In fact, it would be in vain for any one to attempt to practise it, without being thoroughly conversant with the properties of galvanic batteries. The various laws and their applications are not in that order which would have best suited an original paper; as in this work, the laws and the modes of carrying them out, have been first given, and the experiments and facts from which these laws have been deduced, have been subsequently detailed. The inductive reasoning would of course have required an opposite arrangement, but although the last is best adapted for an original paper, the first appears to be preferable for a treatise designed for the use of the operator. It was originally intended to have illustrated the part of this work devoted to the electrotype in all its branches, but it was found that the expense attending such a procedure would have necessarily limited the benefit which I trust the public generally will derive from the work. It has therefore been proposed by Mr. Palmer, who executes the electrotype engravings, to publish a separate work, as an accompaniment to this, and illustrating the application of the electrotype to every species of engraving. This arrangement I instantly complied with, because it allowed this volume to be published earlier, and did not prevent those desirous, from possessing the illustrations; and what is of most importance, allowed the whole of the illustrations to be rendered quite perfect before they were submitted to the public. In these elements I have had frequent occasion to mention works, and enter into arts far removed from my profession, and although I have endeavoured to obtain the best information on these points, yet errors are necessarily liable to occur. For these, the pardon of the reader is entreated, and it is hoped he will recollect that this work is designed expressly to teach electro-metallurgy, and that therefore all matter, not essentially relating to this science is foreign to it. The whole of this treatise may be deemed by many to be quite irrelevant to the business of a surgeon. I cannot, however, but feel, that the most intimate knowledge of natural philosophy and chemistry, should always be combined b with anatomical knowledge by him who ventures to prescribe for the delicate fabric of the human body. In laying this work before the public, I am well aware that it is likely to contain faults and imperfections; the reception, however, which my other original papers have met with, both at home and abroad, has been as favourable as I could have desired, perhaps more so than they deserved. This encourages me to venture again before the public, trusting that the new matter which the present volume contains, will in some measure atone for any errors which may here exist. I must not forget to mention, that these errors have been materially lessened through the kindness of my friend, Mr. John Beadnell, who was so good as to revise the whole of the proof sheets. To my brother-inlaw, Mr. Hutchison, I am also obliged for the analytical index. The principles which are laid down, and the full directions which are given in this work, will be amply sufficient to regulate the proceedings of the operator; but he must recollect that electro-metallurgy is not only a science depending upon ascertained and fixed laws, but also an art, depending for its success upon skill and practice; still, if he follow with patience the processes which are here detailed, I feel assured that he will meet with complete success. BANK OF ENGLAND, Nov. 2nd, 1840. |