CHARRING: A PRESERVATIVE TO TIMBER.

New Zealand Times, Volume XXXI, Issue 4816, 29 August 1876, Page 3

CHARRING: A PRESERVATIVE TO TIMBER.

The following interesting letter was read before the Legislative Council by the Hon. G. M. Waterhouse : “Hobart Town, June, 1876. “ Sib, —Believing that you take an interest in all matters connected with the prosperity of New Zealand, I take the liberty of addressing you on a subject of considerable importance to tho colony,—namely, the construction and maintenance of her harbor works. “For some years past I have continually beard of tho destructiveness of tho ship-worm to the piles forming tho wharves and piers ; but I was rather surprised, on reading a small publication complied in New Zealand in 1875, and containing reports of several gentlemen on the durability of Now Zealand timber, to find the immense expenditure to which the Government have been subjected in consequence of the damage done to the piles by these worms. For tho last seventeen years the Hobart Town Marine Board, at my suggestion

and under my superintendence, have had the piles used in the construction of their works put through a process of charring, and have found it to answer admirably. Some seventeen years ago I was employed by the Government here to superintend the building of, what is called the New Wharf, in this harbor (the old one, tvhich had been erected about fourteen years before, having been quite destroyed by the ravages of the worms oh the piles). The plans, &c., for its erection were all prepared in the Public Works Office, and it was intended to have all the piles to be used in the construction of the wharf coppered ; but on an estimate of cost being made, the intention was abandoned. I then proposed a plan which, from my experience, I considered would answer the purpose of stopping the ravages of the Avorm, viz., to char the piles, the expense of which is not more than 10s. a pile. This being a new process, and apparently so simple a remedy, it was not at first entertained by our Engineering department, and the contractor had orders to proceed with the construction of the wharf. They had driven about six of the new piles well coated Avith coal tar, Avhen on my examining one of the old piles when draAvn but, I found it Avas charred but on one side only. It had evidently been a fallen tree, and a bush fire had passed over the upper side of it, the other side being most likely embedded in Avet scrub or in the ground. The charrred side Avas quite perfect, but the Avorm had completely eaten aAvay the other side of the pile. On this being brought before the department, instructions Avere at once given to the contractor to char all the remaining piles to be used in the work. I am fonvarding you two samples of portions of piles taken from that Avharf, on Avhioh I Avill note particulars. One is a piece of the first pile that was driven without charring, the other from a pile Avhioh was charred and driven a week or so afterwards. I also forward a third piece taken from an old pile Avhich had been driven unchaned about eighteen years ago. This, I think, Avill show that the worm is equally destructive in the Derwent as elsewhere.

“If it is not taxing your time too much, I will give you a short account of how I gained my experience with reference to the benefit of charring piles, and will make a few general remarks. (I may remark, in passing, that my experience was rather dearly bought, as the vessel alluded to was uninsured.) About twelve years before the new wharf was built, I had bought an old whaler of about 300 tons, intending to make a sheer hulk

of her. The necessary alterations were in course of being made, when, by some means, she took fire in the night, and was burnt to the water’s edge. The mainmast had been burnt to less than twelve inches in diameter, when, after being burnt through at the deck, it fell overboard. In making up a raft of old masts for the men to work upon at ships when hove down, this was put in with others. After being about four years in use they became so eaten away that the raft was broken up, and, to my surprise, the old masts, which had been fully twice its diameter, were eaten away to a less size than it, although they had been well coated with hot tar before being put together. The charred spar came out as fresh as the day it was put in, so that, on my undertaking to superintend the building of the wharf, I considered the process of charring would answer better than the coppering, the expense being sp trivial. Since that time I have had the sole charge of the planning and building of all the piers and wharves here. A new pier that was built for the steamboats about ten years since, the piles of which were all charred, are as perfect, to all appearance, as the day they were driven—a standing proof of the utility of this process. I will send a sample from one of its piles with the others. The top of this pier is watertight without caulking, and is subject to the continual traffic of horses, drays, Sec. Some of the main planking was removed lately for inspection, and the beams and main planking were found to be as sound as on the day they were laid. The top is formed with a double thickness of planking, and well coated with chunam between.

“We are just now about completing another new pier about 310 feet in length by 52 feet in breadth, with a curved top nearly the same as a ship’s deck, it will be water-tight, and have scupper-holes to let the water off. It is formed on about 300 piles, the outer ones of 75 feet in length ; it goes into 40 feet of water, and the cost will be about £5,500. By the top being made water-tight, the top planking beams and pile-heads will last many years ; otherwise no wood in the world would stand the weather above ten or twelve years. “ I have no doubt but that your New Zealand timber would, from the accounts I have read of it in the publication referred to, answer every purpose. I notice it complains of our blue-gum not lasting : at this I do not wonder, and much question if the timber alluded to is blue-gum at all. I have seen timber shipped from here as such that was utterly worthless for exposed works.

“We have made many changes from the old plan of wharf-building, saving a considerable expense, and insuring a greater stability and more durability in the upper portion above the water, the particulars of which would occupy too much space in this letter. But, should your Government be inclined to try the experiment, I shall be most happy to furnish them with further particulars. “ His Excellency Mr. Weld has paid a visit to the new pier and witnessed the process of charring, and, I believe, was very favorably impressed with its utility. At the same time he inspected the specimens taken from piles charred and not charred, and which are the same pieces as those lam forwarding to you. —I am, &c., “ John Watson, Late Shipbuilder. “ The Hon. George Waterhouse, Esq.