But my object is not to give more than a cursory account of a few of the most singular of my inventions and improvements; and therefore I shall only glance at one more new invention, which, from its singular utility in carrying into effect the imperial system, deserves partitular notice. It being altogether a novelty, I scarcely know by what name to call it. The instrument which ascertains the interior length of a cask, I term an interiometer, in contradistinction to an instrument for inching of vessels from without, which I term an exteriometer: but as this is for taking of dimensions generally, I sometimes call it an imperial meter; because it is to ascertain the number of gallons or bushels imperial, from the mere invo lution of its dimensions. I sometimes think it ought to be termed an imperial cubit; but as names are of no importance, I will show the utility. This will be obvious from the nature of a simple question and answer; thus, Quere.-1. A vessel being 5.6 meters in length, 4 meters in breadth, and 5 meter in depth, I demand the number of imperial gallons which it would contain? Solution. Gallons contained depth. 5.6 meters, multiplied by Quere.-2. A cylinder being 5.6 meters in diameter, and 4.2 meters in depth, I demand the number of imperial gallons which it would contain? meter. If the question had been bushels, the process would have been just the same; but a bushel meter is exactly twice the length of of a gallon meter: on one edge of a rod are therefore engraven a series of gallon meters, and upon the opposite edge a series of bushel meters;-1, 2, 3, upon the latter standing against 2, 4, 6, upon the former. But in ascertaining the content of cylinders, either in bushels or gallons, the meters consequently of the depths of cylinders are different in their length from the meters used for the diameters, and for the dimensions of angled figures. In consequence of these differences in the lengths of square and circular meters, the former are engraven upon one side of the rod, and the latter upon the other side. And there is the same uniformity between the circular meters for bushels and gallons as exists between the square meter, as before explained, as 2 to 1. And although the superiority of this invention over all others for ascertaining dimensions in terms the most readily introduced into practice, to give the final result, by the pen, will be readily granted; yet I have peculiar satisfaction in being enabled to state, that its greatest advantage is its not requiring computation at all, if the sliding rule be used. And an additional advantage is, that the content for bushel or gallon and from square or circular meter is ascertained by one general operation. It requires no gauge point upon the rule whatever, if an inverted line of numbers be substituted for the ordinary line D; or if the latter line be retained, the gauge point for bushel or gallon from square or circular figures, will be the same in all cases; but, except for ullaging, a one-slide rule is all that is requisite; therefore the advantages are manifold of which this invention is chief. Sliding rules, best suited to the purpose, I have also invented, to accompany the meter, that nothing should be deficient. I will just state, that however important my improvements may be in facilitating different commercial transactions, I think that if the Legislature were to pass a law to compel people to adhere to the just and equitable mode of applying those measures, so that the conclusions might be conformable to common sense, it would be no more than the interests of many of the legislators, as well as thousands besides them, render most imperative. This letter would be too long if I were to enter into an history of the tolerated barbarous perversions of true measures in our na tion! Allow me, gentlemen, to add that, if you will permit me, I will prove, in your next Magazine, that, such is the extent of this evil, a most valuable species of property is depreciated above 20 per cent. I will not only prove that such is the case, but I will also submit a rational theory which shall be capable of I of most effectually obviating such malpractices in future. take this opportunity to express my entire concurrence with the two clauses in the Act for altering of the present weights and measures, which require that tables of equalization and conversion from the quantities and values of present measures to that of the imperial measure, shall be prepared and published. I was so thoroughly convinced of the necessity of this, that I actually prepared tables of equalization and conversion, as to quantity and value, from all the multifarious measures in the British empire to that of the imperial standard. And as the Act is put off until next Session, I mean then to be also prepared with similar tables to convert from all foreign standards to the same standard; thoroughly convinced that, if I am any way seconded in my efforts, I shall be enabled to give to the world one of the greatest advantages, in a commercial point of view, which has ever been submitted to the public. And as I doubt not that truth and equity are the prominent characteristics of your publication, and that you will readily admit the necessity of accuracy, in a great commercial nation like ours, in matters involving the best interests of thousands of its inhabitants, I am persuaded that you will permit me to endeavour, in your next, to obviate the evils of which I complain. I have the honour to be, gentlemen, Your most obedient humble servant, XLV. On an Improvement in the Apparatus for procuring Potassium. By WILLIAM MANDELL, B.D. Fellow of Queen's College. ON repeating the late Professor Tennant's experiment for procuring potassium+, (which differs from the similar one first made by the French chemists, Gay-Lussac and Thenard‡, principally in being more simple and commodious for practice,) it occurred to me, that one part of the apparatus made use of, might, with advantage, be still further simplified: and as every circumstance, however apparently obvious or trivial in itself, which, in any degree, tends to facilitate the production, in greater quantity, of so powerful a chemical agent as potassium, is of importance, I have thought that the mode of From the Cambridge Philosophical Transactions for 1822, Part II. + Philosophical Transactions for 1814, p. 578, to which the reader is referred for the detail of the process. See Phil. Mag. vol. xliii. 457. Annales de Chimie, tom. lxvi. p. 205. operating operating which I pursued might not be wholly unworthy the notice of this Society. It is well known that the grand difficulty in successfully performing the experiment in question, consists in protecting the gun-barrel from the effects of that extreme and long-continued heat, which is necessary to decompound the alkali, and to volatilize its base. The usual practice hitherto has been to surround with a lute*, that portion of the gun-barrel which is introduced into the fire. This operation, however, is always tedious; and although it be conducted even with the greatest care, it is found extremely difficult to prevent fissures in the coating, particularly when the heat is much increased in the course of the experiment. Hence, if eventually the fire have direct access to the barrel, through any crevice which may be formed, the fusion of the denuded part is generally the consequence, and the whole labour of the experiment is lost. This, then, being the common cause of failure, it occurred to me that, if there were substituted for the luting, a thin but sound and well-burnt tube or hollow cylinder of Stourbridge clay, of such dimensions as just to cover that portion of the barrel which is subjected to the fire, the unfortunate result, which I have alluded to, might possibly be avoided. A tube of this description was accordingly procured; and, in order to guard against the hazard of its cracking, by reason of exposure to a sudden increase of temperature, it was, in the first place, gradually and with caution, heated to redness. The remaining part of the experiment was then performed with entire success; and a very considerable quantity of potassium obtained. It may be proper to remark that the hollow cylinder, and that portion of the gun-barrel which it incloses, should be of such relative diameters that, when cool, their corresponding surfaces are not quite in close contact; otherwise, the cylinder will be in danger of bursting, not only on account of its own contraction, but also on account of the simultaneous expansion of the gun-barrel, from the effects of that very high temperature, to which, in this state of combination, they are submitted. Moreover, the whole apparatus should be supported accurately in the same position, throughout the experiment, (by means of rests made of Stourbridge clay,) and should be so * "On couvre cette partie moyenne d'un lut infusible."-Gay-Lussac et Thenard, Ann. de Chim. tom. Ixvi. p. 207. ...... "The lute which I have found most effectual ...... was composed of Stourbridge clay &c."-Tennant, Phil. Trans. for 1814, p. 582. "It (the gun-barrel) is then covered with an infusible lute."-Brande's Manual of Chemistry, p. 184. Ed. 1819. 66 situate situate in the fire, that the materials operated upon may during the whole process be subjected to its greatest intensity. With due attention to these precautions, and to some minor circumstances in the manipulation of the experiment, which I shall not take up the Society's time in detailing, it is believed that the decomposition of potash, by means of iron, might in every instance be effected with almost entire certainty, and potassium be obtained in great abundance. XLVI. On the Origin and Discovery of Iron. By [Continued from page 167.] HOWEVER rude an instrument, in the hands of the early ironmaker, we may in our times consider the blast-bloomery to have been, yet there can be no doubt that in an operation so different from, and so much more complete than, the more ancient air-bloomery, many difficulties attended its general introduction. Prior to this, bellows must have been invented and in common use, and their construction substantial and well understood, before they were made powerful enough to smelt ores of iron. It is also very probable that they were long used to forge the iron produced in the air-bloomery, before they were applied to the department of smelting. Accident alone in almost every instance is the source or cause of invention. Anomalies in the arts and manufactures appear and vanish without notice or attention; and it is only when these fall under the observation of persons of investigating habits, that they are ever philosophically accounted for, or made subservient to useful or beneficial purposes. Bellows, in the first instance, were likely applied in the bloomery upon any occasional diminution of the usual or necessary current of air; by and by some advantage as to quality, produce, or time, might be procured, which would give rise to their more general introduction towards the concluding part of the process, in order more completely to separate the iron from its oxide and from the earths, and to unite the masses more firmly together, to withstand the shock of the hammer. The partial application of the bellows, however, was widely different from its more general application to the purposes of smelting. In the old process the pieces of ore were matured by a long period of cementation; but no perfect fusion or separation took place. The metallic particles coalesced, and part of the oxides and earths were discharged in consequence of their being fusible * Communicated by the Author. Vol. 60. No. 294. Oct. 1822. I i at |