On Preserving Larch Wood. 
375 
The wood which the late Sir Charles G. S. Menteath em- 
ployed for roofing buildings is chiefly Scotch fir. He was 
in the practice ot steeping this wood previous to using it, in a 
strong solution of lime-water for upwards of forty years. Scotch 
fir, that has not been soaked in lime-water, is known to last 
in the roof of buildings very few years ; it soon is preyed upon by 
the worm. 
The method pursued at Closeburn in preparing wood for the 
purposes of building is to saw it into such lengths as the occasion 
demands; next to plunge the planks or beams into a pond of 
lime-water. The pond is made 30 or 40 feet long, 5 or 6 feet 
deep, 16 or 18 feet wide; the bottom and sides are rendered 
water-light. It is then filled with cold water. Before receiving 
the wood, a quantity of fresh-burned hot lime is thrown into the 
pond, which is well stirred with the water to dissolve as mojch as 
possible of it. Into this strongly impregnated solution of lime- 
water the wood, in the various shapes it has been sawn into, is then 
thrown in. As lime-water absorbs carbonic acid from the atmos- 
phere, the lime previously held dissolved in the water, becomes 
insoluble and is slowly abstracted from the water, and deposited 
at the bottom in a solid state, as mild lime or carbonate of lime ; 
hence the necessity of now and then throwing in fresh portions of 
recently-calcined lime, that the water may be resaturated with the 
strongest solution of this caustic alkaline earth. 
With respect to the period that it is necessary to soak the wood 
in lime-water, it must depend very much upon the thickness and 
texture of the wood : roofing-timber of fir will require a fortnight 
or more ; larger and closer-grained wood than the fir ought to be 
in the lime-water pond three or four weeks, or longer time. 
A iter removing the wood from the pond it must be allowed to 
dry and season before it is used. 
Among the benefits that this preparation of wood by the late 
Sir C. G. S. Menteath presents, we may safely enumerate the 
following, viz. : — 
1 . The lime which is absorbed by the pores of the wood appears to 
alter or destroy the albuminous and saccharine principles, and, destroy- 
ing the food of the worm, saves the wood from its ravages. 
2. The two last elements, viz., the albumen and sugar, having been 
so acted upon by the lime, there is less apprehension of its being infected 
by the " dry rot." 
3. The wood, soaked in lime-water, becomes firmer in texture and 
more durable. It is the well-known property of waters holding lime in 
solution, called '■'petrifying wells," to penetrate and deposit upon all 
substances exposed to their influence small crystals of carbonate of lime. 
