Firth. — On the Causes of Fires on Ships. 387 



damp. I laid it on the top of a column stove to dry, directly 

 beside a tin pan containing water which was not boiling, and 

 which never did boil there. I took the charcoal off the stove 

 and laid it on my table. A short time afterwards I discovered 

 it was on fire all through the piece. I laid it aside, and it 

 burned entirely to ashes. The theory of the ignition of char- 

 coal under these circumstances struck me at once. Charcoal 

 has wonderful porosity ; it has the power of analysing air, 

 and of absorbing the oxygen with comparatively little of its 

 nitrogen. The pores of the charcoal were previously filled 

 with moisture. The oxygen of the air was condensed in the 

 charcoal, taking the place of the moisture. The condensation 

 of the oxygen produced heat to ignite the charcoal. I repeated 

 the experiment again, intentionally, watching it carefully, and 

 with the same results." 



Professor Bloxam, one of the most eminent authorities on 

 the spontaneous combustion of charcoal, says, " Charcoal 

 absorbs mechanically into its pores nine times its volume of 

 oxygen. The compression of a gas always evolves heat. 

 Hence the temperature of the charcoal would be raised. If 

 this goes on quicker than the heat is given off (charcoal being 

 a bad conductor of heat, any heat generated in the interior 

 does not escape), then we get spontaneous combustion." 



M. Violette, perhaps the most eminent of French authori- 

 ties on the spontaneous combustion of charcoal, says, "The 

 charcoals from different kinds of wood, when prepared at a 

 nominal heat of 572°, spontaneously ignite between 698° and 

 734°, according to the nature of the wood producing them, but 

 the product from the lighter woods burns quicker than that 

 of the denser woods." M. Violette goes on to say that 

 " charcoals from the same wood, but prepared at increasing 

 temperatures, spontaneously undergo combustion at very un- 

 equal degrees of heat." 



Dr. TJre says, " The higher the temperature at which 

 charcoal has been made, the higher is its igniting-point ; there- 

 fore charcoal made from light woods, such as willow and fir, 

 all of which can be made at a temperature as low as 300° C, 

 are the most dangerous, being both more absorbent and more 

 readily inflainniable." 



Mr. Dupont, the large American powder-manufacturer, 

 states that " charcoal powdered and piled in a heap is liable 

 to spontaneous ignition. He had suffered loss from this cause, 

 and a similar accident occurred in Paris, when one of the 

 wings of the Mint took fire through large quantities of charcoal 

 stored in a garret." 



Mr. Hares, a recognised insurance authority, states that 

 " charcoal is liable to spontaneous combustion, especially in 

 a ground state, when left in heaps and exposed to damp." 



