120 



Selections. 



[NO. 5, NEW SERIES, 



numerous plans nave been proposed, and to some extent tested, 

 for lessening the combustibility of wood, and for covering its sur- 

 face with a protective coating more or less unalterable by fire. 



The simple application of lime or clay- wash, for example, has 

 been found to afford some slight protection to wood, although the 

 tendency of such materials to peel off the surface of the wood (into 

 which they do not in any way penetrate), by exposure to heat, and 

 the rapidity with which the coating is destroyed by atmospheric 

 influence, render them very ineffective agents. 



Several processes have been patented, even recently, for the pro- 

 tection of wood from fire. Some idea of the general nature of such 

 processes will be conveyed by the following extract from an official 

 report made on this subject : — 



" The importance of obtaining an effective method of reducing 

 the combustibility of wood, or even of protecting its surface from 

 fire, has led to an examination into some of the methods of ac- 

 complishing this, which have been lately fpatented, and of the ge- 

 neral nature of which the following is a brief statement. 



I. — " Mr, Maugham's Patent consists in saturating dried wood 

 with an aqueous solution of phosphate of soda and muriate or sul- 

 phate of ammonia, in certain proportions. 



" It is believed by the patentee that these salts will be so affect- 

 ed by each other, and by the action of heat, that the fibres of the 

 wood will be protected by an incombustible coating, while a quan- 

 tity of vapour will be generated by the volatilisation, and partial 

 decomposition, of the ammoniacal salts, which will possess the 

 power of extinguishing flame. 



" The same objects are believed to be obtained by — 



II. — " Lieutenant Jackson's Patent Process, by which wood is im- 

 pregnated with a solution of salts of zinc and of ammonia. 



" The same means are adopted in both of these processes for 

 saturating the wood. 



" It is packed into large cylinders from which the air is then 

 exhausted, the liquid being afterwards forced in with a pressure 

 of 150 to 200 lbs., which is maintained during one or two hours. 



