ON PREVENTING THE DECAY OP WOOD. 337 



coats of the composition should always be given ; and in 

 all compound machinery, the separate parts should be so 

 Tarnished before they are put together ; after which it will 

 be prudent to give a third coating to the joints, or to any 

 other part which is peculiarly exposed to the action of moi- 

 sture, such as water-shoots, flood-gates, the beds of carts, 

 the tops of posts and rails, and all timber which is near or 

 within the ground. Each coat should be dry before the 

 parts are joined, or the last coat applied. 



These compositions are equally efficacious in keeping it would pre- 



iron from decay by rusting. They might also be very ad- serv , e iron » and 



i i j- j • T x- ix xi. , , render arches 



vantageously employed in rendering water-tight the plaster, impervious to 



which is used to case the outside of the arches of vaults water « 

 unsheltered by roofs, provided the mortar were made per- 

 fectly dry, and the covering of the arch brought up to an 

 angle, instead of making it follow the form of the arch in 

 an elipse or the segment of a circle. 



It is necessary to mention, that compositions made of Caution, 

 hot oil should for the sake of security be heated in metallic 

 or glazed earthen vessels in the open air. For whenever 

 oil is brought to the boiling point, or 600° of Fahren- 

 heit's thermometer, the vapour immediately catches fire, 

 although not in contact with any flame; and though a 

 lower degree of temperature than that of boiling should be 

 used in this process, it is not always practicable either ex- 

 actly to regulate the heat, or to prevent the overflowing of 

 the materials, in either of which cases, were the melting 

 performed in a house, the most fatal accidents might 

 follow. 



The following is the proportion of the above ingre- 

 dients, an^ the mode of mixing them, which I should re- 

 commend. 



Take 12 ounces of resin, and 8 ounces of roll brim- Mode of mak- 

 stone, each coarsely powdered, and 3 gallons of train-oil. r,i r the com P°- 

 Heat them slowly, gradually adding 4 ounces of bees'-wax, 

 cut into small bits. Frequently stir the liquor, which, as soon 

 as the solid ingredients are dissolved, will be fit for use. 

 What remains unused will become solid on cooling, and 

 may be remelted on subsequent occasions. 

 Vol. XIX.— Svwmment. Z If 



