In 1737 Mr. Emerson patented a process of saturating timber with _boiled oil_, mixed with poisonous substances; but his process was very little used. This, we believe, was the _first_ patent on wood preserving. About 1740, Mr. Reid proposed to arrest decay by means of a certain _vegetable acid_ (probably pyroligneous acid). The method of using it was by simple immersion. In 1756, Dr. Hales recommended that the planks at the water-line of ships should be soaked in _linseed oil_, to prevent the injury to which wood is subject when alternately exposed to wet and dry; and indeed, many ships were built in which a hollow place was cut in one end of each beam or sternpost, which might constantly be kept filled with _train oil_. Amongst other ships so constructed, the ‘Fame,’ 74, may be mentioned. When, after some years, this ship was repaired, it was found that as far as the oil had penetrated, namely, from 12 to 18 inches from the end, the wood was quite sound, whilst the other parts were more or less decayed. The Americans used to hollow out the tops of their masts in the form of cups or basins; bore holes from the end a considerable way down the masts; pour oil into these; cover them over with lead; and leave the oil to find its way down the capillary vessels to the interior of the timber.[7] In 1769, Mr. Jackson, a London chemist, with a view to the prevention of decay, obtained permission to prepare some timber to be used in the national yards, by immersing it in a solution of _salt water_, _lime_, _muriate of soda_, _potash_, _salts_, &c., the result of which dose was, that several frigates in the Navy subjected to the process were rendered more perishable than if they had been constructed of unprepared timber. The solution was filtered into the wood partly by means of holes made in it. Chapman proposed a similar method of preserving the frames of ships, viz. by boring holes in the timbers, and pumping a _solution of copperas_ in water into them. He believed every part of the vessel would thus be impregnated. Mr. Jackson also prepared the frame of the ship ‘Intrepid’ with another solution. The ship lasted many years. Bowden thought it was a _solution of glue_. Chapman suggested _slaked lime_, thinned with a weak _solution of glue_ for mopping the timbers of a ship. Shortly after Mr. Jackson’s process was started, Mr. Lewis attempted to accomplish the preservation of timber by placing it surrounded by pounded lime, in spaces below the “surface of the earth.” The use of lime has also been advocated by Mr. Knowles, Secretary of the Committee of Surveyors of the Navy, who has written an able work on the ‘Means to be taken to Preserve the British Navy from Dry Rot’ (1821).