Preservation of Wood

Creo-Resinate Process.

The special feature of this process is the mixing of dead oil of coal tar (creosote) with melted resin and formaldehyde. The resin is used to render the wood water proof, and to prevent the washing away of the mixture; and the formaldehyde is used to strengthen the antiseptic nature of the compound. The creo-resinate mixture is applied hot under press ure, and is followed, in another cylinder, by the injection of hot milk-of-lime under pressure, in order to fix and set the creosote.

It is claimed that this process increases the density of the wood and also its resistance to impact and abrasion over either untreated or creosoted wood.* It is further claimed that the more porous blocks take up more of the creo-resinate mixture than the denser ones, and consequently increase in density and strength to a greater degree, the process thus making the blocks more uniform in quality. This is probably true, but only in a slight degree.

Pavements treated by this process have been laid within the past two years in Boston t and Springfield, Mass., and in Balti more, Md., and seem to be giving satisfaction.

Value of Preserved Wood for Payments.

If the pave ment on a particular street is worn out by traffic before the wood has time to decay materially, then except in so far as the treatment adds to its strength, the preservation of the wood will be ineffective; but if the deterioration due to decay is considerable, then the pre servative treatment may add to the life of the pavement. There

is considerable difference of opinion as to the relative value of treated and untreated wood for paving purposes. The relative merits of the two vary with the climate, the amount of traffic, the kind of wood, and the cost of treatment; and an economic solution of this problem is dependent upon the cost of both forms of wood block pavement in comparison with the various other kinds of pavements. Some vestries in London, where there are large areas of both treated and untreated wood-block pavements, favor pre served soft-wood blocks and some =preserved hard-wood blocks— all apparently under substantially the same conditions. Paris, which also has large areas of wood pavements, seems to favor blocks impregnated with 8 to 10 pounds of creosote per cubic foot.

In this country and in London, there has been not a little discussion concerning the relative merits of untreated Australian hard wood and treated soft wood as a paving material for the streets of London.* The engineers of some vestries prefer the one and some the other, hut a significant fact is that the loans made by the London County Council (the central governing board) to the vestries for paving purposes are payable in the case of soft wood paving in 5 years, and in the case of Australian hard-wood in 12 years.