THE RAPID AGEING AND FIREPROOFING OF WOOD. 299 



increase of the heat, the fibrous matter is carbonised slowly and 

 the gaseous products resulting from the decomposition of the salts 

 prevent the ignition of the combustible products proceeding from 

 the calcination of the fibre. In a word, the fire is limited to the 

 points attacked, and is not communicated to the neighbouring 

 fibres. 



The ofiicial tests conducted at Paris by the fire department are 

 conclusive. The inventors constructed a nvimber of cubic boxes, 

 0"50 metre in size, of spruce and poplar firepi-oofed planks, 26 

 millimetres (about an inch) in thickness ; the bottoms of the boxes 

 were perforated with five holes. One of the boxes was filled with 

 a kilogramme (2i lbs.) of dry shavings, which, when set on fire, 

 required five minutes for consumption. A large amount of heat 

 was developed. After combustion, it was found that the outside 

 walls of the box had remained cold, and that the inside had not 

 been charred beyond the thickness of 1 millimetre (y^o inch). No 

 point remained on fire, and no part of the wood was disorganised 

 under the influence of the extreme heat. 



The second box contained a double weight of shavings, which were 

 thirteen minutes in burning. When the combustion was completed, 

 it was found that the interior of the box was red with heat, but 

 there was no flame. 



The third experiment took place with a fireproofed box of white 

 wood, in which 3 kilos of shavings were burned. The test lasted 

 for 30 minutes ; the interior was incandescent and the wood charred 

 for 5 or 6 millimetres (i inch) in depth, while the exterior 

 was simply heated. 



Another test with a spruce box not fireproofed, containing 1 

 kilogramme of shavings, ended in three minutes in a small con- 

 flagration, which had to be extinguished with water. These 

 results are conclusive. 



A piece of fii-eproofed wood submitted to the action of the electric 

 spark is simply carbonised at the parts of contact, while wood not 

 treated bursts quickly into flame. 



Some curious tests on the i"esistance of certain building 

 materials to fire, conducted before the representatives of foreign 

 fire departments, may also be cited. A square construction of 

 cement was filled with 7 or 8 steres ^ of wood moistened with 

 petroleum. It was furnished on one of its sides with an iron door, 



^ 1 stere = 35 cubic feet. 



