over that part of the file which is to receive the first stroke. 3. The nut is then closed, (or the other regulatinggear connected), and the small roller of the pressing lever is made to bear upon the face of the file. 4. The first mover being then put into action, raises and lets fall the apparatus for giving the stroke by which the file receives a cut. And 5. immediately afterwards, or during the same action, as the case may be, (according to the construction as before described), the regulating-gear moves the carriage, and consequently the file, through a determinate space. 6. The cut is then again given; and in this manmer (the strength of cut being duly proportioned to the space between cut and cut), the file becomes cut throughout. 7. The file is then taken out and cut on the other side. 8. The bur is then taken off, or not, as the artist may think best: and the cross-strokes are given over the surfaces as before. And the said machinery by certain slight, necessary, and obvious changes in the structure and disposition of the chizels, and some other of the parts thereof, is adapted to manufacture all other forms and descriptions of files, whether floats, rasps, half-round, three-square, or of any other figure or denomination. In witness whereof, &c. Specification Specification of the Patent granted to JOHN LEACH, of Merton Abbey, in the County of Surrey, Callico-printer ; for a Method of using Malder in the dying of Calicos, Linens, and Stuffs, wherein a considerable Saving is made in the Consumption of that Root or Drug. Dated April 6, 1802. To O all to whom these presents shall come, &c. Now KNOW YE, that I the said John Leach, in obedience to the proviso or condition contained in the said letters patent, do, by this present deed or instrument, under my hand and seal, describe and ascertain the nature of my said invention, of a method for the use of madder in the dying of calicos, linens, and stuffs, whereby a considerable saving in the consumption of that root or drug is made, and the manner in which the same is to be performed; that is to say: That whereas the practice has hitherto been in the dying with madder to use riverwater, pond-water, spring-water, rain-water, or other water, in its natural state, my invention is, that water, being first prepared by heat, either in an open or a steam-tight vessel, will thereby be rendered more efficacious for extracting the tint dye or colour from madder. that this improvement or melioration in the quality or virtue of water for the purpose of dying with madder; may be produced from a less than boiling-heat in an open vessel, and a greater than boiling-heat in a steamtight vessel but that the most sure and certain method to obtain that end in its fullest extent, is to continue the water at a boiling-heat for a certain space of time; and that the efficacy or improved quality in the water will increase in proportion to the time it is kept in a boilingstate; first shewing itself after a few minutes boiling, and VOL. II.-SECOND SERIES. advancing M m 266 Method of obtaining the Salts of Iron advancing progressively for thirty minutes or upwards. That water which has been boiled for the space or time of thirty minutes (little more or less), will be brought to a perfect state for the purpose before mentioned, and that if the boiling be continued for more than thirty minutes, the virtue or efficacy of the water will not be materially improved; and, after boiling thirty minutes, it will be proper to suffer it to cool and subside before it is used, though it will answer very well if used before cooling: and that water, being first prepared by heat as before laid down, may be repeatedly used in the dying with madder, provided the same be preserved from impurities, which may be done by keeping the liquòr, `after boiling or dying with madder, until the vegetable or earthy parts are subsided. In witness whereof, &c. · Account of a Method of obtaining the Salts of Iron at the Minimum of Oxidation. From the JOURNALS of the ROYAL INSTITUTION of THE sulphate, muriate, and acetite of iron, at their minimum of oxidation, may be obtained in a very easy manner, by means of the artificial sulphuret of iron. When artificial sulphuret of iron is acted upon by muriatic acid, or sulphuric acid in a state of dilution, or acetous acid, the sulphureted hydrogene gas, disengaged during the process of solution, prevents any hyperoxygenated salt from being formed by the action of the atmosphere; and a clear fluid, in all cases, of a shade of green, is obtained, which, when freed by heat from any any sulphureted hydrogene dissolved in it, gives a perfectly white precipitate with the alkaline prussiates, and is not found to alter the colour of solution of galls. To form the least oxygenated nitrate of iron, by means of the artificial sulphuret, an acid of a specific gravity, not greater than 1.12, must be used, and the solution must be made without the assistance of heat. After having been freed from sulphureted hydrogene, by being boiled for a minute or two, and then filtrated, it is found similar in its colour and physical properties to the weakest solutions of the other oxygenated salts. When the sulphate and muriate of iron, at the minimum of oxidation, are obtained in the solid form, by evaporation from their solutions, they appear in regular crystals, which in each salt are a different shade of â very pale green colour; their tastes are exactly similar, being astringent, and leaving in the mouth the sensation of sweetness. The least oxygenated nitrate of iron cannot easily be procured pure in the crystallized state, for when the solution of it is heated for any length of time, a new arrangement of its principles takes place; portions of the acid and of the water of the solution are decomposed; in consequence of which ammoniac is formed; and an oxygenated nitrate of iron, with excess of base, is deposited. Amongst the salts of iron, at the minimum of oxidation, I have found the muriate the most convenient, for exhibiting the experiments of Proust, and in eudiometrical processes with nitrous gas. It is more soluble in water than the sulphate, and very much more soluble in alcohol. Practical Observations on the Methods hitherto practised for ventilating Hospitals, Gaols, &c. and Description of an Invention for correcting their admitted Imperfections, By Sir GEORGE ONESIPHORUS PAUL, Bart. With a Plate. From the TRANSACTIONS of the SOCIETY for the Encouragement of ARTS, MANUFACTURES, and COMMERCE. The Thanks of the Society were voted to the Author for this Communication, DESIRING to be understood as not addressing the Society as a claimant of their premium; I conceive I may assist them in the pursuit of their laudable purpose, by submitting to their perusal some practical observations on the modes of ventilation hitherto practised, and by communicating the outline of a design already conceived, and in a limited degree adopted, for correcting their admitted imperfections. It may be necessary to premise, that the peculiar enquiry, the result of which will be detailed in the following pages, was excited by some objections originating in a most respectable quarter, and directed against a system on which I had heretofore solely depended, in providing for the ventilation of such public establishments as have been placed more particularly under my direc tion. It may be inferred from the note annexed to the proposed premium, that similar objections are entertained by the Society: I shall therefore submit my observations, without that delay which would necessarily be occasioned by my modelling them in conformity to the rules you have communicated, and wait |