356 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



years ago, consisted in passing steam into the cylinder, after 

 being charged with the timber in the usual way. Air was then 

 forced in by an air-pump until a pressure of 30 to 40 Ibs. to the 

 square inch was reached. A temperature of 240 to 250 Fahr. 

 was then maintained for some time by the assistance of a coil 

 of steam-pipes in the bottom of the cylinder. When the timber 

 had been subjected to this treatment for a sufficient length of 

 time, determined by experience, the air and vapour within the 

 cylinder were withdrawn. To completely exhaust the sap and 

 moisture, several hours' work with the air-pump was required. 

 When a vacuum of 24 inches was reached, the operation of 

 pumping was suspended, and creosote, oil, heated to a tempera- 

 ture of 200 Fahr., was admitted into the cylinder through 

 perforated pipes ; when the cylinder was full, the pressure was 

 raised to 100 Ibs. on the square inch. 1 



In America, it has been concluded that whatever preservative 

 is to be adopted, the timber for piles subjected to the action of 

 sea-worms should first be charred so as to kill any germs near 

 the surface, open the pores of the wood for the antiseptic, and 

 destroy the nutritive matter on which the worm lives. 2 



The following is the practice of the Eastern Railway Company 

 of France in creosoting timber and sleepers: Sleepers as delivered 

 are stacked and seasoned in the open air. They are then adzed 

 and bored by a special machine, loaded on trucks, and run into 

 a drying- oven, where they remain for twenty-four hours or more. 

 After drying at a temperature of about 176 Fahr., they are run 

 into a metal cylinder 6 feet 3 inches diameter and 36 feet long, 

 which is hermetically closed. The air is then exhausted, and 

 a partial vacuum maintained for about half an hour. Com- 

 munication is then opened with reservoirs of dead oil, which is 

 allowed to flow in at a temperature of 176 Fahr. under pressure. 

 When the oil ceases to flow under moderate pressure, it is forced 

 in by a pump up to a pressure of 83 Ibs. per square inch, and 

 this pressure is maintained for an hour or an hour and a quarter. 

 Communication with the oil-reservoirs is then reopened, and 

 the excess of oil not absorbed by the timber flows back. The 

 cylinders hold 168 sleepers each. The quantity of oil absorbed 

 is determined by measuring the volume of oil before and after 



1 M.P.I.C.E., vol. Ivi. p. 300 ; and Proceeding* of the Engineer*' Club, Philad^l^i^ 

 1879, p. 80. 



2 Scientific American, vol. Ixv. p. 87. 



