as the superintendent thinks necessary. If they remain in the grease an hour, they are found to tin better than when a shorter time is allowed them.

From this pot they are removed, with the grease still adhering to them, into the pot just before spoken of, which contains the body of melted tin; and in this they are placed in a vertical position. Three hundred and thirty-eight, or three hundred and forty plates are usually put into this pot at once; and, for the sake of their being thoroughly tinned, they usually remain in it one hour and a half; but occasionally more time is required to complete this operation.

When the plates have lain a sufficient time immersed in the melted tin, they are taken out and placed upon an iron grating, that the superfluous metal may drain from them; but, notwithstanding this precaution, when they become cold there is always more metal found adhering to them than is necessary; and this is taken off by a subsequent process, called washing. As this process is rather complicated, it will be necessary to describe it with some minuteness.

In the first place, the wash-man prepares an iron pot which he nearly fills with the best grain tin in a melted state-another pot of clean melted tallow, or lard free from salt-a third pot with nothing within it but a grating to receive the plates--and a fourth, called the listing-pot, with a little melted tin in it, about enough to cover the bottom to the depth of a quarter of an inch. The whole will, however, be better understood by referring to the following drawing, which exhibits the several vessels in the order in which they stand in the manufactory, all supported by substantial brick work.

The building in which the pots are fixed is called the Stow. The plates are worked from the right to the left of the stow, as will be evident by attending to the uses of the separate pots. No. 1. represents the tin-pot.

2. The wash-pot with the parting within it.

3. The grease-pot.

4. The pan, containing a grating at the bottom*.

5. The list-pot.

The drawing represents the surface of the pots. The asterisks. shew the places where the workmen stand, and also mark those pots which have heated flues under them. No. 4 has no fire under it.

The parting in the wash-pot No. 2, is a late improvement. The design of it is to keep the dross of the tin from lodging in that part of the vessel where the last dip is given to the plates. By using the common tin in the first process of tinning, much oxide, or dross, adheres to the surface of the plates, and this runs off in the wash-pot, and comes to the face of the new metal -but this parting enables the operator to prevent it from spreading over the whole surface of the pot. Were it not for this parting, the wash-man must skim the oxide off the fluid metal every time he puts plates into it.

The pots, of which I have given a sketch, being all in a state of fitness, the wash-man commences his part of what remains of the business, by putting the plates which have undergone the various operations hitherto described into the vessel of grain-tin called the wash-pot +. The heat of this large body of melted. metal soon melts all the loose tin on the surface of these plates, and so deteriorates the quality of the whole mass, that it is usual, when sixty or seventy boxes have been washed in the grain tin, to take out the quantity of a block, say three hundred weight, and replenish the wash-pot with a fresh block of pure grain tin. These vessels generally hold three blocks each, or about half a

* This pan is designed for the reception of the plates as the boy takes them out of the grease-pot. It has no fire underneath it.

+ None but grain tin is ever put into this vessel, for the whole of the common tin which is consumed in such manufactories, is used in the first process, viz., that which is called tinning.

ton weight of metal. That which is taken out of the wash-pot when it is replenished with pure metal, is given to the tin-man to put into his pot.

When the plates are taken out of the wash-pot, they are carefully brushed on each side with a brush of hemp of a peculiar kind, and made expressly for the purpose. As this part of the business requires considerable adroitness and expedition, it may be worth while to explain it a little more in detail.

The wash-man first takes a few plates out of the wash-pot, and lays them together before him on the stow,―he then takes one plate up with a pair of tongs, which he holds in his left hand, and with a brush held in his right hand brushes one side of the plate, he then turns it, and brushes the other side, and immediately dips it once more into the hot fluid metal in the wash-pot, and without letting it out of the tongs, instantly withdraws it again, and plunges it into the grease-pot (marked No. 3.) adjoining to the wash-pot from whence he had just taken it.

A person who has not seen the operation, can form but a very inadequate idea of the adroitness with which this is performed -practice, however, gives the workman so much expedition, that he is enabled to make good wages, although he obtains only three-pence for the brushing and metallic-washing of 225 plates. I am informed that an expert wash-map, if he makes the best of his time, will wash 25 boxes, consisting of 5,625 plates in twelve hours; notwithstanding every plate must be brushed on both sides, and dipped twice into the pot of melted tin.

Why the plates should be dipped twice during this part of their manufacture, may perhaps require some explanation. It must be recollected that they are brushed quite hot, and before the tin is set, therefore, if they had not the last dip, the marks of the brush would be visible. Moreover, the brush takes the greatest part of the tin off them, so that if they were removed to the grease-pot without being re-dipped, the hot grease would take off what remained.

The only use of the grease-pot is to take off any superfluous metal that may be upon the plates-but this is an operation that requires great attention, because, as the plate is immersed in the

grease while the tin is in a melting, or at least in a soft, state upon it, a part must run off, and the remainder become less and less while the plate continues in it; therefore, if these plates should ever be left in the melted tallow longer than is absolutely necessary, they will doubtless require to be dipped a third time in the tin. On the other hand, if the plates were to be finished without passing through the grease, they would retain too much of the tin, which would be a loss to the manufacturer, and besides, the whole of the tin would appear to be in waves upon the iron.

It is also equally necessary to attend to the temperature of the melted tallow, which must be colder or hotter in proportion as the plates are thicker or thinner; for if, when the tallow is of a proper temperature for a thin plate, a thick one was to be put into it, it would come out, not of the colour of tin as it ought to be, but as yellow as gold. The reason of this is evident. The thick plate contains more heat than a thin one, and consequently requires the tallow to be at a lower temperature. On the contrary, if a parcel of thin plates were to be worked in a pot of tallow which had been prepared for thick plates, such a pot would not be hot enough to effect the intended purpose.

It is a common observation that, in most of our manufactures, and in all chemical speculations, theory and practice are generally at variance; but there are few manufactures, perhaps, where there are so many minutiae which would escape the notice of a casual observer, and yet that require to be carefully attended to, in order to produce a good result, as in that which we have now been describing-and should the perusal of this paper occasion but one individual to pause, who was about to enter into a new concern with which he was only partially acquainted, 1 shall have written to a good purpose.

But to return to the process. When the plates are sufficiently brushed, they are again immersed, one by one, in the pot of melted tin, as has already been remarked, and immediately from this they are put into the pot of tallow above-mentioned. This pot has pins fixed within it, in such a manner as to prevent the plates from touching each other; and this part of the process is conducted in the following manner:

When the wash-man has passed five of the plates through the melted tin, and from thence into the pot of tallow above-mentioned, a boy takes out one of them and puts it into the empty pot to cool, and the wash-man puts in the sixth plate. The boy then takes out a second plate, and lays it to cool likewise, when the man puts in his seventh, and so they go on, in this regular manner, until the whole of the parcel is finished.

In consequence of the plates being immersed in the melted. tin in a vertical position, there is always, when they have become cold, a wire of tin on the lower edge of every plate which is necessary to be removed, and this is done in the following manner :

A boy, called the list-boy, takes the plates when they are cool enough to handle, and puts the lower edge of each, one by one, into the list-pot, which is the vessel that was before described as containing a very small quantity of melted tin, and the same as that which I have marked No. 5. When the wire of tin is melted by this last immersion, the boy takes out the plate, and gives it a smart blow with a thin stick, which disengages the wire of superfluous metal, and this falling off, leaves only a faint stripe in the place where it was attached. This mark may be discovered on every tin plate which is exposed for sale; the workmen, in the manufactory of them, call it the list.

Nothing now remains but to cleanse the plates from the tallow. This is done by means of bran, and as they are cleansed they are put into strong wooden boxes, or boxes of sheet-iron, made exactly to fit them; and this completes the whole business.

ART. XIV. Miscellaneous Intelligence.

I. MECHANICAL SCIENCE.

ASTRONOMY, NAVIGATION, AGRICULTURE, &c.

1. New Comets.-M. Pons, of the Observatory at Marseilles, discovered on the 12th June, a comet in the constellation of Leo; it was very small, being invisible to the unassisted eye, and without any appearance of tail. M. Blanpain, was able to observe it on the 13th, 14th, 15th, 16th, and 19th of the same month; on the 13th at 11 13' 11" mean time, counted from