be as profuse or as economical as you please, and you may have double or treble the light at the same cost as tallow candles; four or five times as much if compared with sperm oil , and above twelve times as much if the comparison be made with wax candles. I know not that any thing can be more satisfactory in favour of any new improvement than a successful issue of a fair and impartial trial; and the results which I have now stated, of a year's trial at the Oldford Works, may, be equally applicable to any other establishment of a similar description. It can hardly be erected on more disadvantageous ground; and if similar success should not ensué, it cannot arise from the planning and execution of the work, but from some other cause wholly unconnected with the nature of the establishment, eitlier from want of consumption, or from improper management, and to which any other concern is equally liable. The great question in the formation of a gas company is, Which is most eligible, coal or oil? Which is likely to absorb the least capital ? Which is ļikely to promise the fairést return? Which is likely to be attended with least loss in case of failure? Which is likely to afford the greatest satisfaction to consumers in general ? To these queries, I do not hesitate for one single moment answering oil gas. There is not a single point in which it has not the most decided advantage; and it is only because these advantages are not generally known, or that they are disallowed owing to the gross misstatements of those interested, that oil gas is not universally adopted. All means are resorted to to cry down oil gas; and I understand that in some of the provincial papers a warm contest has been kept up, and that the opinions of scientific men have been brought forward to prove the incorrectness of the statements concerning the comparative illuminating powers of the two gases. It would be difficult to account for the discrepancy of opinion which exists on this subject (some estimating it as one to two; others as one to two and a half; some again as one to three), if we did not know that the goodness of oil gas depends upon the construction of the apparatus, and the mode of using it, and that oil gas of all the qualities just mentioned may be produced. The gas upon which I have experimented, and upon which the observations I have before made were founded, was produced from works upon a large scale, erected by Messrs. Taylor and Martineau ; and the peculiar excellence of their arrangement is, that the gas produced from the action of their apparatus and retorts is always of à superior quality, which was most satisfactorily proved by Dr. Henry, in his paper read before the Royal Society. It is needless for me here to enter into a detail of experiments which I was trying, and which, for the reasons I have before given, I was reluctantly obliged to give up. I may, perhaps, take some future opportunity of entering more fully into that subject; for me oll ha dis of th the present, I need only say, that the quantity of light may be augmented or diminished by different modifications of burners, by lessening or increasing the pressure of gas, at the same time enlarging or diminishing the external hole through which it passes. Indeed in measuring the proportions of light produced from oil and coal gas, there are so many circumstances to be considered, that no two experimentalists would be satisfied with the results obtained by others. The most satisfactory proof which can be brought forward is the practical result of observations made by a disinterested and intelligent consumer, and which is shown by a computation of pounds, shillings, and pence, more intelligible to those usually interested in gas concerns than all the philosophical or chemical experiments that can be tried. I hope, from what I have above stated, it will not be supposed that I mean to underrate the advantages of science; you, Sir, I am sure, know me well enough, and have been sufficiently acquainted with my pursuits, to exonerate me from such a charge; but the present question is not so much one of science as it is of economy and utility; and in such a question, practical experience would certainly take the lead of scientific experiments. We all know the results of the inquiry on the famous oil question, which will not readily be forgotten. It must have had the effect of teaching the public, that in similar points of dispute, they must look to other authorities than the mere dicta of scientific men; and no authority can be more satisfactory than that which results from the agreement of scientific experiments with practical results. I would have transmitted to you a copy of the report of the Oldford Oil Gas Company, but it is not yet printed: it details the progress of the concern, and expresses the satisfaction of the Committee with the favourable account which they are enabled to lay before the Proprietors, and bears testimony of the correctness of all the statements which were made by Messrs. Taylor and Martineau at the commencement, in all of which they have been fully borne out after a fair and satisfactory trial. I am, yours, &c. M. RICARDO, ARTICLE XIII. Abstract of a Memoir entitled “ An Attempt to ascertain the Chemical Composition of those Minerals which possess the same From Schweigger's Journal, vol. v. New Series. same form and constituent parts. Of this agreement he adduces feldspar and emerald as examples; but there are other minerals, as pyroxene, amphibole, garnet, and mica, which, possessing similar forms, wherever they occur, differ greatly in their composition. This last mentioned circumstance has occasioned great difficulty in arranging minerals according to their composition. It is observed, that M. Mitscherlich has removed much of this difficulty by showing that certain bodies, when containing the same number of atoms, may exchange their places in compounds without inducing any alteration of crystalline form; according to M, Mitscherlich, most oxides which contain two atoms of oxygen are isomorphous; and although his experiinents were made with artificial salts, it is presumed that the same obtains with respect to crystalline minerals. To illustrate this position, M. Rose has observed that the analyses of different specimens of pyroxene show, that all minerals which have the crystalline form of pyroxene are bisiliciates of the four isomorphous bases, lime, magnesia, protoxide of iron, and protoxide of manganese ; in all these, the oxygen of the base is to that of the silica as 1 to 2. If the reasoning of M. Mitscherlich be applied to the analysis of various substances classed by Haüy with pyroxene, it will be observed that they agree in composition with that substance ;-viz. augit, malacolite, sahlite, baikalite, coccolite, alakit, mussite, diopside, and fassaite. The following analyses were made by M. Rose in Prof. Berzelius's laboratory at Stockholm, and most of them were several times repeated; the minerals which possess the crystalline form of pyroxene are classed by M. Rose under the following heads : 1. Pyroxenes with lime and magnesia as bases. 3. Pyroxenes with lime, magnesia, and protoxide of iron, as well as some protoxide of manganese as base. 4. Pyroxenes with lime and protoxide of manganese as basés. 1. Pyroxenes with Lime and Magnesia as Bases. These pyroxenes are mostly white, and form the colourless and usually transparent malacolites, which are sometimes, by slight admixtures, yellowish and greenish. The proportion of lime and magnesia is in almost all which have been analysed very constant, both having the same quantity of oxygen, and together half as much as the silica... White Malacolite from Orrijervi, in Finland. Is white, only greyish when mixed with galena; occurs in large crystalline masses with distinot cleavage , semihard, and very translucent at the edges. Mr. Rose's analysis gives vid! BCE, 225 1823.] *.1 the same Crystalline Form as Pyroxene: 54.64 containing oxygen 27:48 17.0 6.97 2.0 1.08 100.66 Yellow Malacolite from Longbanshyttan, in Wermeland. 55°32 containing oxygen 27.82 6:58 6.46 1:59 Oxide of iron 2:16 !! ates tron, 'the goof ces they lite, 99.07 Ber era M. Hissinger has analysed another malacolite from Longban- 54:18 containing oxygen 27.25 6.89 6:38 2.18 Oxide of iron 1:45 Loss by heating 1.20 99.54 M. Bonsdorf, of Abo, has analysed a white malacolite from Tammare, in Finland, which gave the following results : The Count of Trolle Wachtmeister analysed a white malacolite from Tafel Tyotten, in Norway; its composition was, New Series, Vol. V. the Silica. . 57.40 containing oxygen 28-87 6.48 6.48 0.43 Protoxide of iron. 0.20 97.87 55.40 containing oxygen 27.7 4.4 9.3 manganese 0:43 Alumina.... 2.83 Oxide of iron. 2.50 It tran ke 2. Pyroxenes with Lime and Protoxide of Iron as Bases. Hedenbergit from Tunaberg, in Sadermanland.* The colour is greenish-black; it is semihard in a high degree. 49.01 containing oxygen 24.65 5.86 5.93 2.98 98.94 3. Pyroxenes with Lime, Magnesia, and Protoxide of Iron, as Bases, together with more or less Protoxide of Manganese. In these varieties of the pyroxene, a constant proportion of the bases is wanting ; and there is, therefore, a great variety in the composition. Among all varieties of this series of pyroxenes, there are not two which have their bases combined in the same proportion; even pyroxenes from the same place vary in their composition: all, however, follow the law which M. Rose discovered; It sem dote resu bel 151 * Hedenberg discovered this mineral, which he likewise first analysed. The result of his analysis is, however, very different from M. Rose's. Specimens which were obtained from Prof. Berzelius's collection were first analysed, and afterwards such as M. Rose brought with him from the place. Both analyses agreed completely in their results. |