"1. We had the honourable company's steamer Irrawaddy, moored alongside the Investigator; and having fitted two lead pipes into the Investigator, put them down the fore and after hatchways into the hold.

"2. We had, in the mean time, closed the scuttles of the Investigator's sides, as well as the hatches; moreover, the stern and gallery windows, and the entire front of the poop; boring, at the same time, a hole in each gallery cell, to allow the steam to come up fron the hold into the cuddy. "3. We also fitted a pipe, having a stop-cock on it, to the main hatchway; which was opened occasionally, to observe the state of the steam, in case of danger from its over-pressure.

4. These preparations being made, we had the fires of the Irrawaddy's boiler lighted at eleven A. M., on the 7th ultimo, so as to let on the steam at noon the same day; by six o'clock the same evening, the steam began to show itself at the scuttles, and at the hatches; and the poop and upper deck began to feel hot. We continued the steaming for forty-eight hours, by which time the whole of the decks and sides, even to the outside copper, close to the water's edge, was so heated, as to be scarcely touchable by the hand.

"5, On opening the hatches, to ascertain the result of the operation, we were pleased to see the effectual manner in which the penetrating effect of the steam had destroyed the vermin. The white ants appeared reduced to a substance like soap; and the cock-roaches and rats to a soft pulp, capable of being washed down into the limbers.

" 6. The putrid smell of animal decomposition came on at the end of twenty-four hours, but did not continue above a day.

"7. The paint on the beams and sides was shrivelled, and peeled off; and the leather which covered the ring bolts in the cuddy, was converted into charcoal.

"8. We have purposely delayed sending in our report, till we could ascertain the effect of the steaming on the

caulking, a matter regarding which we were anxious, inasmuch as, if that had been disturbed, the operation would, in future, have had to be confined to a ship about to undergo repair in dock. We have, however, satisfaction in being able to report, that we can discover no injurious effect on the caulking; further, that the steaming a ship for the destruction of vermin, seems perfectly feasible, either afloat or in dock; whether about to undergo repair, or to proceed to sea. The only circumstance demanding attention in the latter case, is, that the ship will require new painting.

"9. Although the destruction of vermin by steaming, may be resorted to under all circumstances, yet the steaming of vessels in dock, previous to their undergoing their usual quinquennial repair of caulking and coppering, will be the most desirable.

"10. In addition to the advantages already noticed, the facility of introducing the steam from below; and the absence of condensation by the water in contact with the whole surface of the immersed bottom, when afloat, will enable the steam to effect its object in one-third less time.

"11. The present experiment having enabled us to ascertain an efficient and simple method of steaming ships, to destroy vermin; we beg here to record our opinion, that, in all moderately large ships, about to be steamed, the masts and bowsprit ought to be taken out, as also all projecting boomkins, davits, and cat-heads. The whole of the hammock stantions, and external birthing, should also be taken away; and the ship be cleared of all lumber, and articles likely to sustain injury from the steam.

12.

For large ships, where the unmasting would be laborious, we conceive that long bags, made of painted canvass, might be put over the mast heads, and be nailed to the deck; and the steam be then admitted into the bags. Painted canvass also might be tacked with wooden battens to the deck, and to the outside, enclosing the sides all round; and this might be extended to hawse-chocks,

quarter-galleries, and to all parts which it would be inconvenient to remove.

"13. By lifting the ship's pumps about three feet, one of them may be fitted as a steam-valve, and the other as a safety air-valve, and thus a communication be made quickly with the lower part of the hold. The steam pipes should be long enough to introduce the steam into the bottom of the hold; as, otherwise, the steam and heat would be, for a long time, intercepted from reaching the lower parts of the vessel, by a stratum of air.

"14. Such of the steamers as may be intended to be used for steaming ships, might conveniently, and at a small expense, be provided with a spare boiler, man-hole cover.

"15. The whole apparatus for steaming could easily be transferred to any one of the steamers, and would then be available for any ship. Independently of the man-hole cover, the parts would merely consist of two pipes of copper, fitted with stop-cocks, of five inches in diameter; together with a steam safety-valve pipe, for the ship about to undergo the process*.

"16. In steaming ships afloat, it will obviously occur to hang the steamer on to the vessel to be steamed; and then so to secure the two, as to prevent the cross motion, their being separately moored would cause, to the injury of the steam pipes. For steaming ships in dock, it will be requisite to have a boiler set so near to the dock, as to admit of having pipes fitted, for the conveyance of the steam to the ship.

"17. It will be requisite, when the steam has been admitted into a ship, whether it be afloat or in dock, to have, a cauldron of boiling water ready, to kill those insects which may attempt to escape; and it will also be requisite to have a few persons in attendance, to shut up those places where the steam shows itself; as well as to attend to the state of the pipes, and of their operation.

* Partial condensation, such as in the case of the Investigator led to the fracture of the upper deck pillais, would, by these valves, be effectually guarded against.

"18. We come now to the consideration of the vast importance to shipping in tropical climates, which this successful experiment of steaming ships to destroy white ants has indicated. The speedy riddance of rats, cock-roaches, centipedes, and scorpions, would alone be of importance. The waste of property by the two first, is very considerable, and fumigation is frequently employed to get rid of them; smoking is dangerous, inasmuch as many ships have been burned in the process; but although smoking kills rats, it will not kill cock-roaches nor ants; neither has it the slightest destructive effect on their eggs; so that while the larger tribe of noxious vermin may be got rid of by this means, the smaller and much more dangerous ones, the white ants, are left to destroy the ship.

"19. Sinking is, no doubt, an effectual measure for the extirpation of those insects; but it is one which can only be resorted to in small ships, and in them even at a considerable risk of entire loss, and at a considerable expence; a great waste of time in the employment of the vessel, and the disadvantage of laying a foundation, by the introduction of mud, for a future more successful attack. In fact, it has invariably been found, that vessels which had been sunk to kill the white ants, were speedily infested afterwards, and rapidly destroyed!

"20. The being enabled to eradicate the white ants from Indian ships, must have the effect of giving an enhanced value to this description of property. It is on record, as well as a truth familiar to the officers of the Marine Department, that several government vessels have been entirely destroyed by the white ants; and further, that by their ravages, great public loss has been sustained; under such circumstances, too much cannot be said in favour of such an application of steam.

"21. The success of the recent experiment may form an era in the history of Indian shipping. The steaming of vessels, to destroy vermin, must speedily come into generaĺ use, Then the only wonder will be, that seeing the

common application of steam to almost every purpose, its excellence, as a substitute for fumigation, was not, in this country, sooner suggested."

It is scarcely necessary to add a word to the above clear detail. The expence of the operation, including the requisite pipes, &c., did not amount to eight hundred sicca rupees; and the subsequent charge for cleaning the ship, was about one hundred. A complete apparatus, to be attached to the boiler, it appears, would not cost above fifteen hundred sicca rupees; after which, the expence would be confined to the expenditure of coals, and the necessary artificers, and contingent charges. One precaution, however, would appear to be necessary to be adopted in the steamvessel, which is, to take care that none of the vermin find their way from the vessel steamed to the steamer. Such appears to have been the case with the Irrawaddy.

Remarks. By the EDITOR.

We think that, in many cases, in tropical countries, this excellent method may be applied, with great success, to the destruction of the white ants, in buildings on shore, where they commit such infinite mischief. A portable steam-boiler might be readily conveyed from one building to another, as occasion required.

XXII.-On making Plaster Casts from Medals. By Mr. W. KELSALL, Engraver, 8, Clarendon Street, Somers Town*.

THE substance most commonly used for forming moulds from medals, and other small works of art, are sulphur, plaster of Paris, and wax. The first of these is, perhaps, in most general use, from the ease with which the mould is made. It is, however, objectionable, as it injures the medal; and, besides, seldom brings the work up with a

* From the Transactions of the Society for the Encouragement of Arts, Manufactures, and Commerce, Adelphi.