194 Forestry Quarterly. 



In spite of the variability of the material, however, many points 

 are clearly demonstrated. The effect of steaming only is shown to 

 decrease the strength of the wood when subsequently wet according 

 to the length of time under treatment or the pressure of the steam. 

 Beyond a certain point in time and pressure a discoloration or 

 scorching of the wood occurs. This limit beyond which scorching 

 occurs depends upon size, quality, kind and moisture condition of 

 the specimens. Seasoned full-sized lobolly pine ties began to dis- 

 color at 30 pounds steam pressure for 4 hours and 20 pounds for 6 

 hours. Green wood stands a greater degree of treatment than dry. 



It will surprise many to learn that this steamed wood when again 

 air dried, provided it has not been scorched, regains the strength of 

 normally seasoned wood, but falls below that of green wood when 

 again resoaked. It appears that the "Fiber-saturation Point" is 

 permanently increased by the steaming process. In fact, as has 

 been shown by tests made at the Yale Forest School, even air drying 

 at normal temperature permanently increases the fiber-saturation 

 point, thus reducing the strength of wet wood. 



The creosote does not decrease the strength, according to these 

 experiments, but it retards the seasoning operation. 



When wood has been pre\'iously steamed and then creosoted, the 

 strength is not less than that of the steamed wood. The creosote 

 likewise retards the re-absorption of moisture. 



The zinc chlorid does not weaken the wood, as shown by the ta- 

 bles, below that of the simply steamed wood, for static loading, but 

 appears to do so for impact stresses. 



A number of tests were made on full sized ties of seasoned lob- 

 lolly pine and western yellow pine, but the results are very erratic 

 or are inconclusive on account of uncertainty as to the exact mois- 

 ture contents. 



Experiments now being conducted by the Forest Service at the 

 timber testing labratory of the Yale Forest School relative to the 

 effect of various processes of drying in air and in steam at different 

 temperatures and pressures should throw further light upon this 

 subject. Great care is used in the selection and preparation of the 

 specimens for the latter tests which was evidently impossible in the 

 case of railway ties. The inherent variability between comparative 

 specimens is thus reduced to a minimum, and the results show great- 

 er regularity. 



The main points of the investigation are clearly recapitulated in 

 the conclusion: 



