Sidebilder
PDF

a memoir on the influence of temperature, pressure, and humidity, on electric phenomena. Jour. de Phys. May, 1816. The experiments and observations are too long for insertion or abridgment. Electricians are much occupied in accounting for the operation of the dry piles of De Luc and Zamboni, of Verona. These attempts at explanation, it is useless to detail: we want facts before the theory can be established; when Gay Lusac thought the explanation very simple, he knew nothing of the experiments of Mr. Brande. In the Annals de Chimie for May, 1816, p. 76, the priority of discovery of the dry pile instead of being given to De Luc, and Zamboni, is attributed to Messrs. Hachette and Desormes, but Brande (Journ. No. 3.) well remarks, that the report of Guyton, Lacroix, and Biot, puts an end to this pretension; “ cette quantite (d’electricité) diminue à mesure que le colle se seche” shows that this could not be considered as a dry pile, permanently electric. The reader doubtless knows that these piles are made of discs of paper, covered with Dutch foil on one side, (this metallic foil being sometimes copper, sometimes silver, zinc, or tin,) and the under side with manganese in very fine powder, made to adhere by thin glue, or gum arabic. The discs are from half an inch diameter to an inch, and in number, from 500 to 2000. They are well made by Mr. Lukens, a very ingenious mechanic of Philadelphia. When two of these piles or columns are used, a ball or a pendulum suspended between them, is alternately attracted from the one to the other, the poles at the top and bottom of the two columns being of opposite electricities. They do not seem to

act in moist weather so well as in dry. The phenomena seem to me to be rather electric than galvanic, for air is more indispensable than moisture; but their theory is not yet understood. The series, is, metal, paper, manganese. The discs are pressed very close together. Zamboni, in 1812, introduced as a covering to the underside of the silvered paper, either olive oil, a dilute solution of honey in water, or a saturated solution of sulphat of zinc, and then sprinkled the powder of black manganese on the unsilvered side of the disc thus treated. Mr. Lukens says, the sulphat of zinc answers best. De Luc's construction was six hundred discs of very thin zinc, alternating with paper covered with Dutch foil, that is, copper; so that the series was zinc, copper, paper. The manganese was employed by Zamboni, in consequence of some experiments of Volta, on the great electro-motive property of this oxyd. M. Schubler says, the activity of the pile is increased by atmospheric humidity; I think I have remarked the opposite fact. But Gay Lusac considers the effect of this pile as dependent on some humidity still retained in the paper, and is weak and slow in consequence of the small quantity retained. This is not inconsistent with a weak action of the pile in a humid atmosphere. The following observations of Mr. Brande, however, deserve much attention: “One fact we will venture as “certain, that the continued action “of two considerable piles of Zam“boni has produced, among many “electric phenomena, one che“mical effect, viz. the abstraction “ of nineteen parts of the oxygen “present in the portion of atmos“ pheric air wherein the columns “ had been hermetically confined, “ and the cessation of all electrical “ phenomena, and of all oscil“lations of the pendulum after “ the absorption of the oxygen. “We shall also venture to assert, * from what we have observed, “ that the oscillations of the pen“ dulum are not in the least af“fected by atmospherical modifi“cations, and that, therefore, the “pile cannot be considered either “as a barometrical or hygrome“ trical instrument. The oscilla“tions in our case were twenty“two in a minute, (the columns “being placed at the distance of “six inches from each other,) and “continuing at the same num“ber till the moment when they “ceased altogether, the pendulum “ remaining in a fierfiendicular flo“sition. On cautiously admitting “ a fresh supply of atmospheric “air, without moving the appara“tus, the pendulum was instantly “ attracted to the positive pole, and the oscillations renewed in “ the same number and progres“sion.” Journ. of Science and the Arts,” No. 3. p. 101. In a paper by Mr. Alexander Walker, in the Annals of Philosophy, for Sept. 1816, a theory of electricity is proposed as depending on the decomposition of atmospheric air into oxygen and nitrogen—and of galvanism on the decomposition of water into oxygen and hydrogen. The memoir is too condensed to admit of abridgment, but it is a very plain and neat collection of the leading facts, in a short compass; and so plausible in its conclusions, as to deserve much consideration.

MINERALOGY AND GEO. LOGY.

It is most unfortanate, that these

branches of knowledge in proportion as they improve by the accumulation of facts, are obscured by the accumulation of names. It is literally true, that it requires more time and attention to become acquainted with the modern synonimy of mineralogy and geology, than with the substances themselves which are meant to be designated. Hauy and his followers, have done infinite mischief by the motley jargon, half Greek and half French which they have introduced without any meaning characteristic of the mineral intended. With pretensions equally well founded, may the Americans borrow from the Creeks or the Choctaws. The nation that first discovers a new country has a right to name it, and if we do not adopt chemical names expressive of the component parts of a mineral, we cannot do better than adhere to the nomenclature of Werner, who is entitled to be considered as the father of mineralogy. In this country his language will be convenient, from so large a part of our population being German. The perpetual changing of old names, amounts at present, to a most oppressive nuisance. Not content with changing the mineralogical nomenclature, the French, rejecting at first the transition rocks of Werner, have at length been compelled to admit them as intermediaires between their primitive and secondary; but they have given them new names as usual; the grauwackes are now psannmites, and the shistose rocks of primitive or transition origin, are now phullades: I suppose, as containing vegetable impressions. Primitive, transition, and secondary, are certainly appellations founded on theory, which a single shell in a granite rock would

everthrow: I grant that compound, chrystallized, inclined rocks, void of organic remains,—compound inclined rocks of mechanical mixture by deposition, imperfectly or minutely chrystallized with very few organic remains,—and horizontal rocks containing animal remains in abundance, would be freer perhaps, from objection; but, until Werner's theory be actually overthrown, I see no good reason for quitting either it, or its language. The whole of Hauy's theory of chrystallization, which threatened to confine mineralogy to mathematical formulae, and microscopic investigation, and convert a cabinet of minerals into a plaything for young gentlemen and ladies, has received a shock from the dissonance between similarity of primitive form, and similarity of chemical composition in many cases, particularly in the arragonite, which the late analysis of Bucholz and Meissner, in Schweigger's Journal, Ann. de Ch. June, 1816. p. 176, show to be very frequently void of any trace of strontian, and in many cases, containing this earth in quantities so small, that it can only be considered as accidental; contrary to the statements of Stromeyer and Gehlen, whose discovery of strontian in the arragonite was supposed fully to account for all its anomalous chrystallization. The late analysis of the Rev. Mr. J. Holme, affords little assistance. The angles of many chrystals determined by Hauy, have been corrected by the more accurate goniometer of Wollaston, as in the chrystals of quartz, and of sulphat of barytes, by W. Philips, Esq., in his paper before the Geological Society, noticed in Thomson's Annals, Feb. 1816. To these may be added the re

marks of La Metherie on the augite, cocolite, sahlite, allalite, massite, and erzoliter-and on the sulphurets of silver, lead, and iron; Journ. de Phys. Jan. 1816. 27. To a Geologist, a specimen of a country continuing the same for fifty miles together, is a good and valuable specimen: to a modern mineralogist, a specimen is valuable, if it be so beautiful and so rare, as to be a curiosity in these respects; it is esteemed in proportion as it is useless; and it is considered as still more valuable, if it require the skill of a lapidary to cut it, a microscope to discern its external figure, a goniometer to take its angles, and a complex mathematical formula to express in how many possible ways its external form might have arisen by additions to, or defalcations from, its primitive chrystal. I am aware, that, in many cases the chrystal aids in determining the mineral, but so seldom chrystals are perfect, that the man who wishes to be a mineralogist, must principally rely on geognostic situation, on the Wernerian characters, and on chemical analysis. Chrystallography is best fitted for amateurs, and to be employed on a lady's cabinet. But the most serious obstacle to Hauy’s system, is, a late paper of M. Methuon, abridged by Mr. Grenville, in the first number of Brande’s Journal. The author insists, that chrystals are not the re-sult of undisturbed solution or fusion, but the produce of a peculiar decomposition of amorphous chrystallizable matter, in contact with air, and the ordinary atmospheric moisture; the particles of this matter during decomposition arrange themselves according to certain laws of attraction, not yet accurately determined; the process is carried on in the dry way, in the air. M. Methuon gives a history of his discovery of such chrystals gradually formed from chrystallizable matter during his residence at Elba: of his pursuing the same investigations with full success, by the gradual formation of chrystals from shapeless chrystallizable matter, on the chimneypiece in his own apartments, on his return; such as alalite, garnet, green idocrase, pyroxene, peridot and pyrites. He describes how any one else, by a few months patience, may obtain the same results. He deduces from these facts the following corollaries; 1. Chrystals begin to form at their summit edges and solid angles. 2. Nature produces, by direct process, all simple and compound chrystals, without first forming any nucleus. 3. The matter serving to form chrystals, is in the state of a solid mass before, and continues in that state during the whole process. It is the chrystallizable matter. 4. This matter is that, which, by infiltration, has filled the chasms and clefts of mountains, and the cavities of rocks; which composes veins, stalactites, and stalagmites, and, in general, all that is found in the form of blocks and nodules, in the midst of large masses. To hasten artificially the production of chrystals out of his chrystallizable matter, he makes it into balls, incloses a number of them in a space surrounded by a slight wall of loose bricks, waters them once in two or three days, so as to keep up merely a state of constant but moderate humidity, and examines them every fortnight, and changes their places, putting those above that were before below. Every person who has attended

to the phenomena, and the growth of drusy chrystals of quartz, on the surface of quartzose stones lying loose on shistose and secondary mountains, and of the veins of calc spar in limestone, will readily agree to the probability of M. Methuon’s statement. One of our best and most accurate mineralogists in Philadelphia, has assured me, that he has repeatedly observed similar facts, and possesses similar specimens in his own collection. M. Hauy has published (Ann. de Ch. April, 1816. 447.) some observations on pyro-electric minerals, the oxyd of zinc, some Spanish tourmalins, and Siberian topazes. Thomson's Annals for April, 1816, has given the analysis of a flexible small grained sandstone from China; flexible when wet, silex 95.40; lime, with a trace of iron 3.10; alumina 0.50 E 100. Dr. Meade, of Philadelphia, has a specimen of course grained flexible sandstone, which he found last summer in the neighbourhood of lebanon, New York state. Quere, are not all the granular dolomite limestones elastic when wet, as well as the Pittsfield marble? (Pittsfield, Massachusets.) Dr. Thomson is a strenuous supporter of the atomic theory of Dalton: I know not where two men more able are to be found; and what they urge is truly entitled to respectful consideration. But, the proposition that the particle A has a strong affinity for, a violent inclination to combine with 4 particles of B, but not the slightest for 3 particles, is, at first blush, so revolting to common notions, that it requires strong proof to make it out. This proof has not been given; we have a few coincidences and more approxi

[ocr errors][merged small][merged small]
[ocr errors][ocr errors][ocr errors]

and proven, even in his Elements of Agriculture, where the reader is left to find out the use of them, he certainly somewhat outsteps the line of demonstration. Chemistry seems fast verging into a science of arithmetical and mathematical calculation instead of experiment; and questions are now decided by the Rule of Three, that ought to have no test but the weight and measure of actual analysis.

Mr. Brande has, in his second number, reviewed with some sharpness the “..Attempt to esta“blish a flure scientific system of MINE RA Locr; by the electro che“mical theory, and the chemical “firofortions, by J. Jacob Berze“lius, of Stockholm.” Perhaps Mr. Brande’s able review of this work may be too vituperative, but I confess, I read the work of Berzelius carefully, without deriving from it any clear ideas, so confused did it seem in its facts and applications, and so needlessly abstruse throughout. It contains no mark of the clear head, the distinct and manifest application of facts to the theory, which distinguish the writings of Dalton and Thomson.

Dalton, Thomson, and Davy, seem to insist on the atomic theory as regulated by the weights of the atoms; Berzelius in solids, and Gay Lusac in gases, insist on the bulk or volume as a regulator of the multiple combination. The whole of the atomic theory is extremely ingenious, and perhaps its defenders have rendered it probable; but we have not yet a sufficient induction of accurate facts to establish it fully.

Vol. I.

Mr. Hume of Long Acre was, I believe, the first chemist that assigned oxygen as the basis of silex; and numerous-facts look that way. Berzelius in his new system of mineralogy treats silica as an acid, and speaks with perfect decision of the siliciates, bisiliciates, trisiliciates, &c. The facts have not yet duly prepared us for this language. In geology, A. H. de Bonnard has given a geognostic description of the Erzgebirge. The rocks observed are, 1st. Granites, six varieties: one like that of Cornwall alternating with mica-schist, and containing tin. Another passing into eurite (weisstein, white stone). Another alternating with psammite and phullade (grauwacke,and primitive and transition schist). Another also containing tin, forming a transverse mass in gneiss. Another alternating with mica-schist, and gneiss. Another forming veins (filons) and shooting into the mica-schist and gneiss. He is inclined to consider these as so many distinct formations. 2. Eurite, weisstein, white stone, usually confounded with gneiss. It consists of a. Very fine granular feldspar, sometimes almost compact, colour grayish-white or yellowish. b. Brown mica in various proportions: when this is abundant the rock is stratified, fissile, the feldspar friable like dolomite; it is otherwise when the feldspar is compact, and the mica in small proportions. c. It incloses garnets generally, sometimes disthene, and other mixed or disseminated minerals. d. Sometimes this rock incloses a granitoid, passing into graK

[graphic]
« ForrigeFortsett »