484 



PROCEEDINGS OF THE AMERICAN ACADEMY 



From these I selected a variety of samples differing most widely in 

 their physical properties and appearance, and examined with most care 

 those portions which were most decayed. While it was evident that 

 a large variation in the size of the piece of wood taken produced a 

 corresponding variation in the ignition point, it seemed to me advisable 

 to determine at the outset the comparative points of ignition of the 

 various portions, using in each case pieces of approximately the same 

 size, and subsequently to determine the vai-iation caused by taking 

 larger pieces. In the following determinations pieces of wood measur- 

 ing about 1.6 cubic centimeters were used, and since the wood was 

 very light they weighed about half a gram each. 



A. Inside Wood, sound. 



B. Inside Wood, sound. 



300 failed. 

 305 " 

 318 « 

 330 ignited. 



C. (6.) Inside. 



o 



248 ignited. 

 243 " 

 242 " 

 238 " 

 230 failed. 



D. (a.) Sap-wood, decayed fibrous. 



D. (b.) Sap-wood, decayed fibrous. 



228 ignited. 



226 '^ 

 222 " 

 218 " 

 218 " 

 215 failed. 



(e.) 238 ignited. 



224 failed. 

 (d.) 235 ignited. 



227 failed. 



