OP ARTS AND SCIENCES. 



487 



it was found that the iguition point was materially lowered. The 

 specific gravity of the wood obtained by measurement varied some- 

 what, but was not far from 0.3. 



It will be seen that the point of ignition with 0.5 gram of the wood 

 was 204°; with 3 grams, 181°; with 9 grams, 175°; and with 16 

 grams, 158°. The dimensions of my air-bath were such that no larger 

 pieces of the wood could be used, and, moreover, from the material at 

 my command it was impossible to obtain larger compact pieces of this 

 particular sort of wood. It would seem probable, however, that with 

 larger masses of this porous wood ignition could easily be started by 

 a much lower initial temperature. 



