The _petroleum_ oil-wells, near Prome, in Burmah, have been in use from time immemorial. Wood, both for ship-building and house-building, is invariably saturated or coated with the product of those wells; and it is stated that the result is _entire immunity from decay_ and the ravages of the white ant. At Marseilles, and some other ports in the Mediterranean, it used to be the practice to run the petroleum, which is obtained near the banks of the Rhone, into the vacancies between the timbers of the vessels, to give them durability. It was sometimes, for the conjoint purpose of giving stability and duration to vessels, mixed with coarse sand or other extraneous matters, and run in whilst hot between the ceiling and bottom plank, where it filled up the vacancies between the timbers in the round of their bottoms, excepting where necessary to be prevented. The great objection to the use of petroleum is its inflammability. _Creosote_, its great rival for wood preserving, is also inflammable, and not so agreeable in colour; but it is _considerably cheaper_, which is an important matter. As we are now about to enter upon the subject of patent processes, &c., it appears desirable to lay down certain principles at the commencement, in order to assist the reader as much as possible. Almost every chemical principle or compound of any plausibility has been suggested in the course of the last hundred and fifty years; but the multiplicity and contradiction of opinions form nearly an inextricable labyrinth. To commence. 1st. It seems obvious that _the sooner the sap is wholly removed from the wood the better_, _provided the woody fibre solidifies without injury_. 2nd. That _the wood should be impregnated with any strongly antiseptic and non-deliquescent matter_, _which must necessarily be in solution when it enters the wood_. No deliquescent remedy is eligible, because moisture is injurious to metallic fastenings. 3rd. _The wood should be first dried, and its pores then closed with any substance impervious to air and moisture, and at the same time highly repellant to putrescency._ The most essential requisites in a preservative of timber being a disposition to _dryness_, and a tendency to resist _combustion_ as far as consistently obtainable. 4th. _Any process to be successful ought not to be tedious, very difficult, or too expensive._ These are important elements in the success of any patent. Very little is known of any preservative process previous to the year 1717, when directions were given by the Navy authorities to _boil_ treenails, and dry them before they were used. But whether the custom had prevailed before this time, or whether their strength and durability were increased by it, there are no means of ascertaining. It does not appear that any substance was put into the water to decompose the juices; but as they are soluble in warm water, perhaps the power of vegetation might have been destroyed without it.