of Timber J especially Oak^ Sfc. 



85 



during a sharp frost, and alternately frozen and thawed ten or 

 twelve times, by which their relative powers of resisting varia- 

 tions of temperature will be tested ; as by the former experi- 

 ments it is proposed to ascertain their capacities for enduring 

 the change from humidity to drought. In the trials which I had 

 made this last winter, the specimens of Norway and French oak, 

 though both good of their kind, after being frozen eight times 

 exhibited the appearance shewn in the accompanying sketch : 



while the English, submitted to similar ordeals for the same 

 periods, and at the same times, withstood the effects both of 

 drought and moisture, heat and cold, with but little change, I 

 might almost say totally unhurt; of .t^ifi the second figure may 

 serve as an example. .< , . j,,. ,,+ ,. 



(The medullary rays, which pass downward from right to left, are, however, in 

 the wood-cut, certainly too strongly marked.) 



Other similar specimens were also steeped in a saturated 

 solution of Glauber's salt, and then the salt allowed to crys- 

 tallize, which process, alternated with the dissolving of the crys- 

 tallized salt, was repeated several times with an effect similar 

 to, though less powerful than, the frost ; fig. 3. has been drawa 

 from a specimen thus treated. 



It would be wrong, as i have before observed, to generalize too 

 boldly from the few trials already made, which, however, have 

 been sufficiently numerous and satisfactory in their results to 

 encourage the belief that the experiments detailed promise 



