570 



DETAILS OF CONSTRUCTION. 



lb. of sulphate of zinc, 15 lb. sulphate of 

 iron, 12 lb. sulphate of copper, are to be 

 pounded and dissolved in hot water, and 

 then one quart of sulphuric acid is to be 

 added to the mixture. The above, added 

 to 36 gallons of water, is ready for use. 

 The timber is steeped in a tank for the 

 following periods : 1-inch deal, three 

 days; 3-inch plank, seven days; 5 to 7 inch 

 plank, twelve to fourteen days; and 12 

 to 14 inch square timber, twenty-one days. 



BetheWs preparation for preserving tim- 

 ber, consists of creosote, along with coal 

 tar or other bituminous matter. 40 gal- 

 lons are required for a load of timber 

 of the pine kinds ; a less quantity is 

 required for the closer-grained woods. 

 Creosote is rapidly absorbed by the tim- 

 ber, even to the centre of the plank or 

 log. Wood saturated with creosote is 

 not only said to be more durable, but to 

 become almost waterproof, and is fit for 

 use a few days after the process is com- 

 pleted, about which time it loses its dis- 

 agreeable smell. 



Dr Boitckerie's method consists in em- 

 ploying impure pyrolignite of iron, in 

 spring, when the ascent of the natural 

 sap begins. The process is as follows : 

 Near the bottom of the trunk a hole is 

 bored through its diameter, into which a 

 thick-toothed narrow saw is introduced, 

 and with it the trunk is cut through to 

 within about an inch of the outside, 

 working the saw first to the right-hand 

 side, and then towards the left, so as to 

 cut through the greater part of the sap 

 vessels. The opening thus made is then 

 carefully covered with pitch-cloth, leav- 

 ing only a small hole, through which a 

 pipe is placed, communicating between 

 the trunk of the tree and a reservoir con- 

 taining the pyrolignite of iron. During 

 summer or autumn a large tree will by 

 this operation become completely satur- 

 ated with the mineral fluid in the course 

 of a few days, as at these seasons the 

 vital forces of the tree are in full activity. 

 When smaller trees, or ordinary-sized 

 branches, are to be operated upon, their 

 lower ends are immersed in the fluid. 

 In winter the operation is thus per- 

 formed : The timber being cut into con- 

 venient lengths, a waterproof funnel is 

 secured to the top end of each, containing 

 the liquid ; and the solution is said not 

 only to force its way down through the 



wood, but at the same time to drive out 

 of it all the sap and air it contains. The 

 operation is deemed complete when the 

 preparation begins to issue from the 

 lower end of the log. The quantity of 

 mineral liquid used is stated to be one- 

 fifteenth part of the weight of the green 

 wood. 



The most certain way of preserving 

 timber is to procure it of proper age and 

 maturity, and to place it so in buildings 

 that it may have sufficient ventilation. 



Other methods besides those above 

 stated have been adopted, such as steep- 

 ing the wood, previous to use, in water, 

 and afterwards drying it in the sun and 

 air ; subjecting it to the action of steam, 

 and then drying it; boiling it in water 

 in long troughs heated by steam or 

 flues ; removing the atmospheric pres- 

 sure, and at the same time applying arti- 

 ficial heat, so as to promote evaporation. 

 The object of all these operations is to 

 remove, by extraction and evaporation, 

 what is called the sap, or the watery part 

 of the alburnum, or last formed layers 

 of the wood, which are found to decay 

 sooner than the interior and firmer, 

 or less porous layers. The immaturely 

 formed timber decays first, and no paint- 

 ing whatever will prevent it ; nay, paint- 

 ing timber in this state only hastens its 

 decay by preventing the natural sap from 

 finding its way out. Charring is a reme- 

 dy, but that can only be applied to timber 

 used for the roughest of all purposes ; and 

 yet, although the advantage of charring 

 posts to be set in the ground has been 

 known for ages, how seldom do we see it 

 reduced to practice ! 



Boyd and Miller's antisceptic mineral 

 black paint has been recommended by 

 architects for saturating the ends of 

 beams let into walls, posts set in the 

 ground, &o, as a remedy against decay ; 

 and also for iron work, to prevent rust ; 

 and for cordage and canvass, to render 

 them durable, as well as to correct the 

 dampness in walls. 



The principal cause of decay in timber, 

 we believe, is pretty generally admitted to 

 be the felling it at an improper season. 

 This season appears to be the spring, when 

 the sap is in a peculiar state, and highly 

 disposed to ferment, when it can no longer 

 flow through the tissues. Over timber 

 cut in our own country we have complete 



