guide the student to a considerable extent in their methodical consideration. Belonging to mineralogy, are the subjects, blow-pipe, geology with its subordinate rocks, ores, and meteorolite. The medical student may read with advantage, the articles, acid (arsenious,) antimony, bile, blood, calculus (urinary), the sequel of copper, digestion, gall-stones, galvanism, intestinal concretion, lead, mercury, poisons, respiration, urine, &c. The agriculturist will find details not unworthy of his attention, under the articles, absorbent, analysis of soils, carbonate, lime, manure, and soils. Among the discussions interesting to manufacturers are, acetic, and other acids, alcohol, alum, ammonia, beer, bleaching, bread, caloric, coal, and coalgas, distillation, dyeing, ether, fat, fermentation, glass, ink, iron, ores, potash, pottery, salt, soap, soda, steel, sugar, tanning, &c. The general reader will find, it is hoped, instruction blended with entertainment, in the articles, aërostation, air, climate, combustion, congelation, dew, electricity, equivalents, galvanism, geology, light, meteorolite, rain, and several other articles formerly noticed. It may be proper now to say something concerning the execution of the present Work. In the month of June, a gentleman from London, who had become possessed of the copy-right of Nicholson's Dictionary, waited on me in Glasgow, requesting that I would superintend the revision of a new edition, which he purposed immediately to send to the press. I stated to him, that, however valuable Nicholson's compilation might have been at its appearance in 1808, the science of chemistry had undergone such alterations since, as would require a Dictionary to be written in a great measure anew. To this he replied, that the above work had enjoyed great popularity; that he was certain a new edition of it would be well received; that he did not expect me to compose original articles or dissertations, but merely to add, from recent publications, such notices of new discoveries and improvements as might seem proper, and to retrench what appeared obsolete or useless; taking care to comprise the whole in such a compass as would render the price moderate, and thus place the book within the reach of manufacturers, medical students, and general readers. The terms offered appearing reasonable relative to the work required, I entered into an engagement to revise the new edition in time for the winter classes. Having assembled complete series of all the British scientific journals, with several of the foreign, and the various chemical compilations from Newman and Macquer, to the present day, I commenced the stipulated revision. I had advanced a very little way, however, when I became alarmed at the dilemna in which I found myself placed. A large proportion of the articles which I had reckoned on reprinting, as having undergone little change since 1808, were found to have been quite obsolete at that period. They had been evidently copied, with scarcely any alteration, through Nicholson's quarto Dictionary, from Macquer and Newman, back I believe to the era of Stahl, Becher, and Agricola. Under the article acid (acetic), 36 pages of Crell's Annals had been copied verbatim et seriatim on the concentration of vinegar by charcoal, &c. A larger space was allotted to the separation of silver, under the articles silver, parting, and assay, than was dedicated to all the gases and earths. The article CALORIC was meagre and vapid, while desulphuration or roasting of pyrites, Brazil wood, and safflower, occupied a far greater extent. Putrefaction consisted of extracts from Becher's subterranean world, and other details belonging to a former age of chemistry. The contents of the 8vo Dictionary were made up from four sources. 1st, From his quarto Dictionary of 1795. The long article Ores, for b X example, was taken chiefly from Cramer, while the labours of Klaproth and Vauquelin were seldom noticed. Large excerpts were also given from obsolete Dispensatories, concerning substances of no chemical importance, and destitute of all medicinal power. 2d, From the contemporary systems of Brongniart, Henry, Murray, Thomson, &c. about another fourth was copied in continuous articles. This formed the best part of the whole. 3d, Large excerpts were given from his own Journal, quite disproportionate to the rest of the work, and to the exclusion of numerous interesting topics. Indeed a journalist, who compiles a system, has great temptations to fall into this practice. 4th, The fourth portion was composed by himself. This seems to have constituted about one-twentieth of the Dictionary, and related chiefly to physics, in which he was experimentally versant. These articles were very respectable, and have been in some measure retained; see Attraction, Balance, Hydrometer, and Laboratory. What follows the first asterisk in Attraction, has been now added. Mr. Nicholson was indeed a man of candour, intelligence, and ingenuity. His original papers on electricity, and mechanical science, do him much honour; and the abstracts of experimental chemical memoirs, which he occasionally drew up for his Journal, were ably executed. Had he bestowed corresponding pains on his 8vo Dictionary, my present task would have been greatly lighter. After making such a survey, the feelings under which I began to labour were similar to those of an architect, who having undertaken to repair a building within a certain period, by replacing a few unsightly or mouldering stones, finds himself, on his first operations, overwhelmed in its rubbish. Reverence to public opinion, and anxiety to fulfil my engagement, however irksome, have induced me to make every possible exertion to restore the edifice, and renew the decayed parts with solid materials. If it has not all the symmetry, or compactness, of an original design, leisurely executed, still I trust it will prove not altogether unworthy the attention of the chemical world. I have investigated the foundation of almost every fact or statement which it contains, and believe they merit general confidence. Many inaccurate positions and deductions, in our most elaborate modern system, I have taken the liberty of pointing out; aware that the influence of Dr. Thomson's name and manner is capable of giving considerable currency to his opinions, however erroneous they may be. His industry deserves the highest praise; and his chemical experience would entitle his decisions to deference, were they less precipitate, and less dogmatical. Many of my embarrassments in compiling the present volume, have arisen from his contradictory judgments, pronounced in the Annals of Philosophy; see ACIDS PHOSPHORIC, PRUSSIC, &c. If under the influence of the feelings thus excited, a hasty expression has escaped me in the ardour of composition, I hope it will not be imputed to personal animosity. I have always lived on amicable terms with this distinguished chemist, and trust to continue so to do. Perhaps in commenting on his opinions, I may have unconsciously caught the plain manner of his criticisms. My sole object, however, was the establishment of truth. The refutation of error was undertaken, only when its existence seemed incompatible with that object. On our other valuable systematic works, I have made no critique, because Dr. Thomson's is the most comprehensive, professedly taken from original memoirs, and of highest authority. I have long meditated to publish a methodical treatise on chemistry, in which both its study and practice would be greatly simplified, and its applications to the phenomena of nature, medicine, and the arts, faithfully detailed. In my memoir on sulphuric acid, inserted in the Journal of Science and the Arts, for October 1817, is the following passage: " I was led to examine the subject very minutely, in preparing for publication a general system of chemical instructions, to enable apothecaries, manufacturing chemists, and dealers, to practise analysis with accuracy and despatch, as far as their respective arts and callings require. I hope that this work will soon appear. Meanwhile, the following details will afford a specimen of the experimental researches executed with this view." The three years and a half which have elapsed since the above paper was composed, would have enabled me to fulfil the promise, but for various unforeseen interruptions to my labours. If the public, after this larger specimen of my chemical studies, shall deem me qualified for the task, I may promise its completion within a year from this date. The work will be comprised in four octavo volumes, and will contain the results of numerous investigations into the various objects of practical chemistry, joined to a systematic view of its principles. By several simple instruments, tables, and rules of calculation, chemical analysis, the highest and most intricate part of the science, may, I apprehend, be, in many cases, brought within the reach of the busy manufacturer; while, by the same means, such accuracy and despatch may be insured, as to render the analysis of saline mixtures, complex minerals, and mineral waters, the work of an hour or two; the proportions of the constituents being determined to one part in the thousand. In prosecution of this plan of simplifying analysis, I contrived, about five years ago, an alkalimeter and acidimeter. Being then connected by a biennial engagement with the Belfast Academical Institution, I was occasionally called upon to examine the barillas and potashes so extensively employed in the linen manufacture, the staple trade of Ireland. I was sorry to observe, that while these materials of bleaching differed excessively in their qualities, no means was possessed by those who imported or who used them, of ascertaining their value; and that a generous people, with whom every stranger becomes a friend, frequently paid an exorbitant price for adulterated articles. The method which I devised for analyzing alkaline and acid matter, was laid before the Honourable Linen Board in Dublin, and by them referred to a competent chemical tribunal. The most decisive testimonies of its accuracy and importance were given by that tribunal; and it was finally submitted, by desire of the Board, to a public meeting of bleachers assembled at Belfast. Unexceptionable documents of its practicability and value were thence returned to Dublin, accompanied by an official request, that measures might immediately be taken to introduce the method into general use. Descroizilles had several years before described, in the Annales de Chimie, an alkalimeter, but so clumsy, operose, and indirect, as to be not at all adapted to the purposes of the linen manufacture. My instrument, indeed, was founded, as well as his, on the old principle of neutralizing alkali with acid; but in every other respect it was different. After spending about two months on this project, and no answer being returned either to the public request of the bleachers, or to my own memorial, I set off on an intended tour to France, and have never since resumed the negotiation.* The terms on which I had offered the instrument, were merely honorary; for the sum proposed, would not have repaid the expense of my journey and attendance. However important there * The Right Hon. John Foster, who took the chief direction of the Board, showed me every possible attention; but from the absence of many of its members in England, a quorum could not be assembled at the time. fore the adoption of that instrument was to Ireland, it was of no pecuniary importance whatever to me. Of the two hundred and ten thousand pounds expended that year (1815-1816) on imported alkalies, a very large proportion might have been saved by the application of my alkalimeter; and what is perhaps of more consequence, the alkaline leys used in bleaching, would, by its means, have been rendered of a regulated strength, suited to the stage of the process, and fabric of the cloth. What would we say of a company, who imported spirituous liquors to an enormous amount, and paid for them all as proof, though they were diluted with fifty per cent. of water? Now, though this neglect of the hydrometer would have a happy moral influence on the consumer, it would be vastly absurd in the dealer. No such apology can be offered for neglecting the alkalimeter. The following is an extract from the Belfast News-Letter of July 9, 1816: " I now submit the following document to public inspection, and humbly ask, whether any such experiment has been ever made publicly before; or whether there is described in any publication prior to my late exhibition in Dublin, and in the Linen Hall of Belfast, an instrument by which it can be performed? "This day, one of the porters of the Linen Hall, Belfast, was called into the Library-room, at the request of Dr. Ure, who, being quite unknown to Dr. Ure, and never having seen any experiments made with acids and alkalies, he took the instrument at our desire, which, being filled with coloured acid, by pouring it slowly on adulterated alkali, which we had previously prepared, he ascertained exactly the per centage of genuine alkali in the mixture. - Belfast, 25th June, 1816. (Signed) JOHN S. FERGUSON, Chairman... "The above experiment did not occupy the porter above five minutes. I believe it is a new document, though, after the egg has been placed on end, others will set to work to do the same. "Though the instrument was entirely the result of my own experiments -and calculations, I never claimed a greater share in its invention, than I hope its peculiarity merits. The following excerpt from a letter addressed to the Right Hon. John Foster, prior to any public discussion on its merits, will satisfy the public on this head. "Dublin, June 12, 1816. "SIR, In the letter which I had yesterday the honour of addressing you, I omitted some scientific details, which I now beg leave to submit to your consideration. That the quantity of alkali, present in any portion of potash or barilla, is directly proportional to the quantity of acid requisite to produce saturation, is a fact which has been known for upwards of a century to every chemist, and forms a fundamental law of his science. In establishing my instrument on this law, the principle of it may be said not to be new." &c. "The practicat application of the established laws of nature, or of the general deductions of science, to the uses of life, is, perhaps, the most beneficial and meritorious employment of the philosophic mind. The novelty which I lay claim to in my contrivance, is this, that it enables a person versant neither in chemical researches nor in arithmetical computation, to determine by inspection of a scale, as simple as that of a thermometer, the purity or value to one part in the hundred, of the alkalies, oil of vitriol, and oxymuriate of lime, so extensively, and often so injudiciously employed by the linen-bleacher." In my journey through England to France, I submitted my Essay on Alkalimetry, &c. to Dr. Henry, in the confidence of friendship, and under the injunction of secrecy. From the unreserved communication of ideas, however, which subsists between this chemist and his townsman Mr. Dalton, he soon gave him a perusal of the Essay. In the then existing edition of Dr. Henry's Elements, Descroizilles' plan for testing alkalies was alone given; in the edition published since, he has inserted four supplementary pages entitled, "Improved Alkalimeter and Acidimeter." This instrument is essentially mine, very slightly disguised. He concludes by saying, "No chemical operation can be more simple, or more easily managed, than the measurement of the strength of alkalies by acid liquors, and of acids by alkaline ones, in the way which has been described." This is exactly Columbus's egg, or Roger Bacon's gunpowder; et sic facies tonitru, SI SCIAS ARTIFICIUM. By comparing his new way taken from my Essay, with the methods which he formerly gave, the world will see whence the simplification originated. I offered to give him an abridged account of my plan, for insertion in his Elements, after my negotiation about the alkalimeter was finished. Without consulting me on the subject, he publishes to the whole world, what he conceives to be the essence of my improvement.* Two motives have hitherto withheld me from laying the instrument before the public. First, a desire to render it as complete as possible; and secondly, an expectation, that the Honourable Board, who superintend the linen manufactures of Ireland with extensive powers, might wish that an instrument originally presented to them, and which is capable of giving light and precision to all the processes of bleaching, should appear under their auspices. As it now exists, the instrument is greatly superior to that described by Dr. Henry. For the commercial alkalies and acids, I use only two test liquids and one scale; and these are such, that a man unacquainted with science, may prepare the first, and verify the second. The instrument is at once an alkalimeter, an acidimeter, a complete lactometer, a nitrometer for estimating the value of nitre, an indigometer for ascertaining the dyeing quality of indigo, and a blanchimeter for measuring the bleaching power of oxymuriate (chloride) of lime and potash. With it, a busy manufacturer or illiterate workman may solve all these useful problems in a few minutes; and many others, such as the composition of alloys of silver, of copper, tin, lead, &c. the purity of white lead, and other pigments. It is, moreover, a convenient hydrometer, comprehending in its range, light and heavy liquids, from ether to oil of vitriol; and is particularly adapted to take the specific gravity of soils. It may be said, that the solution of the above problems may be accomplished by any skilful chemist. But surely, in a manufacturing nation, the person who brings the science of Klaproth, Sir H. Davy, Dr. Wollaston, and M. Gay-Lussac, into the workshop of the manufacturer, is not a useless member of the community. The result of numerous researches made with that view, has shown me the possibility of rendering analysis in general, a much easier, quicker, and more certain operation, than it seems hitherto to have been, in ordi * It would seem that Dr. Ure has since been satisfied that Dr. Henry intended him no injustice, as this gentleman has explained to him, that in a passage of his Elements, "page 512, vol ii. he intended to give Dr. Ure the credit of inventing an instrument on the principle of directly, and without calculation, indicating the per centage of alkali in any specimen, and that he pretended to nothing more than a modification of Dr. Ure's method" See Letter of Dr. Ure, in the Journal of Science, No. 22, p. 401, July, 1820.-American Editor. : |