Previous to Boucherie’s method, a German, Frantz Moll, in 1835, proposed to introduce into wood _creosote in a state of vapour_, but the process was found to be too expensive. This was a modification of Maconochie and Lukin’s trials in 1805 and 1811.[11] A similar process has since arisen in New York: we believe Mr. Renwick, of that place, suggested it. Such were the known labours, when Dr. Boucherie, in December, 1837, devoted his time to a series of experiments upon timber, with a view to discover some preservative process which should answer the following requirements: First, for protecting wood from dry rot or wet rot; second, for increasing its hardness; third, for preserving and developing its flexibility and elasticity; fourth, for preventing its decay, and the fissures that result from it, when, after having been used in construction, it is left exposed to the variations of the atmosphere; fifth, for giving it various and enduring colours and odours; and sixth and last, for greatly reducing its inflammability. It is a curious coincidence that at Bordeaux, in 1733, the Academy received a memoir relative to the circulation of the sap and coloured liquids in plants; and it was at Bordeaux, a century afterwards, viz. 1837, that M. Boucherie first mentioned his method. M. Boucherie’s process was first discussed in Paris in June, 1840. It consists in causing a solution of _sulphate of copper_ to penetrate to the interior of freshly cut woods, to preserve them from decay; he occasionally used the chloride of calcium, the _pyrolignite of iron_ (_pyrolignite brut de fer_), _prussiate of iron_, _prussiate of copper_, and various other metallic salts. As a general rule sulphate of copper is used; but when the hardness of the wood is desired to be increased, pyrolignite of iron is taken (1 gallon of iron to 6 gallons of water); and when the object is to render the wood flexible, elastic, and at the same time uninflammable, chloride of calcium is used. The liquid is taken up by the tree either whilst growing in the earth or immediately after it has been felled. Not more than two or three months should be allowed to elapse before the timber is operated upon, but the sooner it undergoes the process after being felled the better.