52 ANNUAL OF SCIENTIFIC DISCOVERY. 



% 



The blue vitriol is absorbed more readily by the hemlock, and the oaks 



prefer the pyrolignite. 



For the impregnation of the heavy timbers used upon bridges and other 

 structures, a large wooden cistern, 4 feet diameter in the clear, and 27 feet 

 deep, was constructed of three-inch seasoned white-pine plank, tightly 

 caulked in the scams, and bound with iron hoops; two courses of three-inch 

 plank were laid transversely, and firmly secured at the bottom of the cistern. 

 This, when finished by the carpenter^, was sunk into the ground, until the 

 top edge stood three feet above the surface. A hoisting crane is used in lift- 

 ing the timber; the sticks being placed in a vertical position in the cistern, 

 which should always be kept filled to its top edge with the solution, in this 

 way a pressure of a column of 27 feet in height is maintained at the but-end 

 of the timber. 



The following table shows the quantity of solution introduced into a cubic 

 foot of the different woods, the solution consisting of one part of pyrolignite 

 of iron and six parts of water: 



Timber freshly cut will receive the solutions more readily than when dry. 

 Some pieces of white oak, which had been felled three months, absorbed per 

 cubic foot, 70 per cent, more than the same description and sizes of timber 

 which had been twelve months felled. It was also observed that in pushing 

 some freshly-cut beams, with a sudden downward force, into the cistern, the 

 sap would appear on the top of the beam, often in quantities to fill a wine- 

 glass. 



These facts confirm the opinions of Boucheric, and show that the drying 

 and seasoning of timber, to prepare it for impregnation, is an unnecessary 

 waste of labor. The expense of impregnating railway timber, with the pro- 

 cess advocated by the Avriter, is but trifling. The labor required is involved 

 only in lifting and carrying the timber; and to this must be added the cost 

 of the solutions absorbed. A statement of the cost of preserving sills with 

 the usual antiseptics is here given. 



CHLOIUDE OF ZIKC. 



In proportions used by Brunei, viz., one pound to 10 gallons of water cost of 

 chloride of zinc, 9 cents per pound. 



Labor at tank, lifting and carrying the sills, 1-0 cent. 



Solution absorbed, 2 gallons, 1-8 '' 



Cost per sill, 2-8 " 



BLUE VITRIOL. 



In the proportion adopted by Boucherie, viz., one pound to 12^ gallons of water 

 cost of blue vitriol, 14 cents per pound. 



Labor at tank, etc., 1-0 cei;t. 



Solution absorbed, 2 24 " 



Cost per sill, 3-24 " 



