escape of gas. To agitate the materials, there is fixed in the still a stirrer, consisting of a square frame of wood covered with lead. From the still there runs a bent tube to convey the gas to the receiver for the alkaline solutions. But before it is admitted into this, it passes into a small circular vessel, which is, according to the proportion of the apparatus, from twelve to eighteen inches diameter, and contains water in order to arrest any uncombined chlorine which may arise in the process; but since the water bath has been substituted for the sand bath, this seldom occurs. The gas is then admitted into a large receiver, charged with the alkaline, or calcareous solution, intended to receive and absorb the chlorine gas which comes from the still, and when sufficiently saturated it is drawn off by a brass cock fixed at about two inches from the bottom of the receiver. The receiver

is of a square form, or that of an inverted cone, and is made of lead, where the capacity does not exceed 120 gallons, and of wood lined with lead, when the business is extensive. It is closely covered at top, and has a hole for introducing water into the receiver with a leaden plug. In some manufactories, two or three false bottoms made of lead are laid on brackets of the same metal fixed to the side of the receiver. These false bottoms are perforated, or made of spar work, in order to spread the chlorine through the water during distillation. The solution is constantly stirred, to promote the absorption of the gas, by an agitator, which, in large works, is driven by a power from a steam engine. (Parkes. Ramsay.)

In recovering alkali from waste leys, it is found more economical to construct what are called stone boilers, than to employ vessels either of lead or iron. Stone boilers

are large oblong chambers, whose lateral walls are about two feet high, and are built into the ground to prevent their giving way. The outside wall is well rammed with tempered clay puddle to prevent leakage. An arch of brick is thrown over between the walls, which is covered with mortar to retain the heat. Proper openings are at the same time left, by which to examine the state of the liquid; these are covered with a plate of iron. At one end of the chamber, a furnace of a sufficient capacity is built, having a breast work interposed between it and the liquid, over which the flame plays. At the other end of the chamber, a vent of sufficient height is built to carry off the smoke. The fire being lighted, the flame plays along the surface of the liquid, which by this means is evaporated. Some of these stone boilers are so capacious as to contain 10,000 gallons. (Ramsay.)

When stone boilers are not used, common evaporating pans may be employed, and particularly in works of moderate extent. After the leys have been brought to a due consistence, the materials are removed to a small reverberatory furnace and gently calcined. A common baker's oven is well adapted for this purpose, and is used, as we learn from Des Charmes, (p. 87,) in the manufactories in France. If the former is preferred, the process should, if possible, be continued night and day; or, at least, the fires should be raked up at night, and the passages of the chimnies carefully stopped. Furnaces which are thus wrought, will last seven times as long as those where it is not attended to; insomuch as the contraction of the materials, during the time of cooling, and their subsequent expansion, wear them rapidly out. (Parkes.)

To avoid the inconvenience and

injury arising from the escape of the noxious vapours of chlorine from the bleaching liquors, and to have the goods more equally exposed than in the old mode of stratifying them above one another in large vessels, Mr. Rupp of Manchester contrived an apparatus extremely simple and ingenious. It consists of an oblong deal cistern, made water tight, with two perpendicular beams, made to turn round on their axes, and each furnished at the lower end with a plain pulley of a large diameter. On one of these beams the cloth is rolled after the pieces are slightly sewed together. The cistern is filled with the bleaching liquor, and the cloth is wound by means of a winch from one beam to another several times successively, so as to expose the whole of its surface equally to the fluid.

I shall conclude this part of my subject with a few practical notices, which are of importance to be attended to in conducting extensive bleaching manufactories.

1. When boilers are set in brick work, care should be taken not to make the fire places too large, for when the bars are not entirely covered with fuel, the cold air rushes in from the ash pit, between the uncovered bars, and counteracts the effects of the heat. Fire places should be no larger than is barely necessary for fuel to produce the intended effect. They should be so constructed also, that the whole bottom of the boiler be exposed to the action of the burning fuel, and that the whole of the flame and heated air actually impinge upon the bottom before they reach the sides to pass to the chimney; for the heat applied to the bottom will be infinitely more effective than that applied to the sides. To aid this, some large stills and coppers are made with the bottom to pro

ject inwards, presenting a concave surface to the flame; some have, for the same purpose, a flue of 10 or 30 inches diameter running through them. (Parkes.)

2. As cast iron is so liable to break from its unequal expansion when submitted to heat, steam engine boilers are now usually made at a great expense, with plates of wrought iron rivetted together, which, in the end, come to be cheaper, from their greater durability. But much expense might be saved by making the upper part of cast iron, as it does not suffer from the action of fire. This might be done by screws, and when the old bottom was worn out, it could be removed and a new one put in its place. The vessel would then be as good as at first. (Parkes.)

3. In works where large and expensive iron boilers are used, sulphurous coals ought to be avoided if possible, as the sulphur rises during combustion, unites with the iron of the boiler, and forms a sulphuret of that metal, which wastes away as fast as it is formed, and soon renders the boiler totally useless. (Parkes.)

4. In places where peat is to be had, it is an economical fuel in manufactories. In some places of Scotland, we are told by Mr. Mushet, (Phil. Mag. VII. p. 44,) that it can easily be procured at a shilling per ton, and four tons of dried peat, as he distinctly shows, will make something more than one ton of peat char, a substance which produces a much stronger fire than coals or coke. M. Sage informs us, that he found, by repeated experiments, that the turf char produces a heat nearly in the proportion of 3 to 1 of the best charcoal. But while we can say this much, we must not conceal that it is not easy to make peat char, as it requires a peculiarity of management

which can only be acquired by considerable experience. (Parkes.)

Lead,

5. A great deal of the sheet lead in the market is manufactured from old lead, and, consequently, contains solder and other impurities. Such lead ought carefully to be avoided in the construction of retorts and chambers; for a small portion of tin or plumber's solder will reduce the melting point of the metal very considerably. for example, melts at 6120 Fah. but with of tin, the melting point is at 558°; with, at 5550; and with, at 530o. Upon the same principles, Des Charmes cautions the manufacturer against joining any of his lead vessels by soldering, and recommends the fusing of the parts to be joined, as preferable; for," says he, "in process of time the solder, though ever so strong, yet because it contains tin, is liable to excessive corrosion by chlorine, which is not found to attack lead, even when heated in any sensible degree." But if it cannot be managed without solder, the parts soldered must be defended by several coats of white lead, putty, resin, or pitch mixed with bee's wax, any of which experience proves to effectually answer the end. Lead is sometimes used for lining or securing parts of the kier which are thought to be in danger of leaking. Now, the sulphur which is always contained more or less in potash, acts upon lead, forms a sulphuret, which being of a red colour, is liable to produce stains. (Parkes.)

6. I shall here mention a circumstance which, although it may seem trivial, is of some importance; namely, that in the roofs of bucking houses there should not, as there

1 Mr. Mushet has written several very instructive papers on this subject: see particularly Phil. Mag. vol. XXXII.

sometimes is, be any iron nails; for the steam from the boiling vessels will be condensed by the tiles, and the water thence arising will wash off from the nails the oxide which it contributes to form, and this falling on the cloth will produce stains, of whose origin the workmen may often be at a loss to discover the cause. No iron ought to be used in the roof of a bleaching house, nor any lime on the inner side of the walls. (Parkes.)

7. As some of the vessels in the bleaching process may, when fuel is scarce, be heated by steam, and as in every case dryers and other parts of the apparatus are actually so heated, it will be useful to mention, that as charcoal is a very slow conductor of caloric, in proportion to dry sand as 3 to 2, all those vessels which are heated by steam, if they were made double, and the space between the outer and the inner vessel filled with ground charcoal, the heat would be so prevented from escaping, and any one particular temperature might be kept up for a great length of time, and make a material saving in fuel. (Parkes.)

8. Since the adoption of the dry oxymuriate of lime, the distilling apparatus is less used than formerly, as the bleachers buy this salt ready prepared. It is still used, however, in making oxymuriates of the alkalies. In this process, it is of the utmost importance to attend to careful luting; so much so, that Des Charmes affirms, (page 4,) "that the single obstacle of not knowing how to manage lutes, is quite sufficient to repel the efforts of the most zealous in this kind of operation." To compose the fat lute of the chemists, take any quantity of good grey or blue clay, or fuller's earth, and dry it in thin cakes in an oven; then pound it finely and sift it; beat a sufficient

the circulation of the blood; Mr. Browne had lectured three evenings on the law of patent rights; and Dr. Griffiths had commenced a series of lectures on the diseases incident to the labouring classes of the community. This system of instruction it was intended should continue throughout the winter

season.

Besides this there was a prospect of practical lectures on different arts; and, as a commencement, the committee announce in their report, that a lecture on the art of Pottery was to be delivered by a gentleman practically conversant with it.

Considerable attention had been bestowed on the formation of the mineralogical collection and library; and also to the establishment of a cabinet of models. The architectural models were provided, which were of great importance to Mr. Strickland in the illustration of his lectures. Several of the mechanical models had been executed, and contracts for the preparation of the remainder had been entered into. The sum of 300 dollars had been expended during last year for this object, and this did not include those making at the time of the

the success or promotion of American manufactures were invited to contribute. The exhibition far exceeded the expectations of the committee; was generally visited by the members of the Institute, and by the public at large; and was of great benefit to the Institute by gaining for it an immense accession of members. It is intended that another exhibition shall take place in October next. To excite a higher emulation among the mechanics and manufacturers, a list of premiums, to be awarded at the exhibition, was prepared and circulated, and of these the committee had the pleasure of awarding fourteen. A list of eighty-three premiums has been published, which are to be awarded at the exhibition in October 1825; and there can be little doubt that these, and the additional time for preparation, will render the second exhibition much superior to the first.

There can be little question as to the success of an Institution commenced so prosperously; and the rapid accession of members which it has received, clearly shows the interest taken in its prosperity by the good people of Philadelphia. There were at the commencement of this year, the names of upwards of six hundred individuals entered as members of the Institute.

ON DRAINING OLD WASTES

IN COAL MINES.

GENTLEMEN,-I am a reader of your Magazine, though not a mechanic, and from it I have frequently received both instruction and entertainment; of its utility I need say nothing, better judges having long ago given their opinion. In some of the late Numbers, I observe a controversy has arisen on the mode of draining old wastes in coal mines. The discussion has originated, I perceive, in

this query

a query by a Coal Hewer; is answered by G. M., and G. M.'s answer is replied to by S. S. and by A. K. J. The propositions of G. M. if they had been understood in the manner in which he entertained his ideas on the subject, I believe there might, in some sense, have been little or no cause for calling his views in question. A question may be, whether the parties had similar ideas respecting the purport and meaning of the query. G. M.'s ideas of the nature of that query, may