oct. — dec. 1857.] Mode of protecting Timber from Fire. 121 



It is the same method as that employed in patent processes for 

 preserving timber from decay. 



" I am not aware whether Mr. Maugham's process has been sub- 

 mitted to any extensive practical test. Numerous experiments 

 were however instituted on Lieutenant Jackson's process, under 

 the direction of Mr. Brunel. 



" Specimens of seventeen different kinds of wood were prepared ; 

 corresponding pieces being kept unprepared, and others covered * 

 with a coating of paint. Their powers of resisting fire were tested 

 by piling the prepared, unprepared and painted specimens round a 

 perforated sheet iron surface, filled to the top with a bright coke 

 fire. 



" In most cases the prepared wood resisted the action of fire for 

 a longer period, and, when removed from the fire, ceased burning 

 sooner than the unprepared specimens. 



" It was also evident that light porous woods were more effi- 

 ciently protected than those of a denser character. 



" There is no doubt therefore that the combustibility of wood is 

 more or less diminished by either of the above methods of treat- 

 ment, although the protective acticn must be ascribed to the in- 

 destructible compounds with which the wood is to some extent im- 

 pregnated, far more than to the vapours evolved by the decompo- 

 sition of the small quantities of ammoniacal salts forced into the 

 wood. 



" Although by the impregnating process adopted in the above 

 patents, the preparative solution is believed to be forced into the 

 very centre of the wood, it is essential, if such a result is to be 

 obtained, that the solution should be weak, since it is impossible 

 to force strong saline solutions thoroughly into wood. 



" It is evident that the protective action of the salt cannot, under 

 these circumstances, be very powerful. 



" Were it possible, on the other hand, to employ stronger so- 

 lutions, the expense of the processes would be considerable. 



"The necessity of costly apparatus for impregnating the wood is 

 also a matter of serious moment." 



