The preservation of timber from decay is a subject that very early occupied the attention of engineers and all those interested in railways. A railway sleeper is particularly exposed to deterioration the lower portion being surrounded with moist ballast, whilst the top portion is more or less uncovered--two different conditions in the same piece of timber. Several processes have been tried, such as Kyanizing, Burnetizing, Boucherizing, etc., but the system which has given the best results, and is now almost universally adopted, is that known as creosoting. This method consists of forcing liquid creosote, under considerable pressure, into sleepers or railway timbers which have been prepared or dried by ordinary natural seasoning or by special artificial means. Creosote is a dark, oily liquid, distilled 212 from coal tar, varying in its composition according to the quality of the coal from which it is obtained, and ranging in its specific gravity from 11·08 to 10·28. Creosote oils of light specific gravity were at one time in favour, but experience proved that, to some extent, the light oils were volatile and also soluble in water, and that heavy rains washed out the constituents which were essential for the preservation of the timber. On the other hand, by heating the heavy oils and using high pressure the napthaline which is dissolved only by the heat, is forced into the wood, fills the pores, and solidifies. Creosote is obtainable in large quantities, at prices varying from twopence to fourpence per gallon, according to the demand and cost of production. Newly delivered sleepers or railway timber contain so much sap or water that it is impossible to force a sufficient quantity of creosote into them until they are properly seasoned or dried. The seasoning is generally arranged by sawing each block into two sleepers, and then stacking the sleepers on edge in tiers, leaving a space of four or five inches between each of them for a proper circulation of air. The sleepers should then be left for nine to twelve months to season, although more may be necessary in some cases if the blocks were particularly wet at the time they were sawn. When ready for the process the sleepers are placed in the creosoting cylinder, which is generally about 60 feet long by 6 feet in diameter with semi-spherical ends. One of the ends is fitted with strong hinges and fastenings, and forms the doorway. The sleepers are packed carefully inside, and the doorway made tight. The machinery is then set to work to exhaust the air from the cylinder and allow the creosote to flow in amongst the sleepers. When the cylinder is full the force-pumps are started to force in more creosote up to the pressure prearranged and regulated by the safety-valve, in some cases 100, 110, or 120 lbs. per square inch. The creosote should be heated to 112° or 120° Fah., to dissolve the napthaline and reduce all the component parts to a thoroughly fluid condition.