RESISTANCE OF HARDWOODS TO CREOSOTE. 11 



creosote. In oak, hickory, and sycamore, for example, the rays were 

 conspicuous because of their resistance to penetration in marked con- 

 trast to the surrounding treated tissue. 



SPRINGWOOD AND SUMMERWOOD. 



In the hardwoods the effect of springwood or summerwood on 

 treatment was not so important as the effect of the peculiarities of 

 the different types of structure and the arrangement of the elements, 

 such as vessels, fibers, rays, etc. In very heavy treatments the creo- 

 sote not only passed through the cavities or lumena of the cells in both 

 spring and summer wood, but sometimes penetrated the walls. 



CONDITION OF GRAIN. 



More or less difficulty was experienced in treating the woods in 

 which the fibers were interlaced or cross-grained. 



DENSITY. 



The ease or difficulty of securing a satisfactory penetration does not 

 appear to depend upon the density. Woods having high specific 

 gravities were sometimes treated with greater ease than species of 

 much lower specific gravity, and vice versa. 



RADIAL, TANGENTIAL, AND LONGITUDINAL PENETRATION. 



In most of the species tested the radial and tangential penetrations 

 were very much less than the longitudinal penetration. In general, 

 the species that were difficult to treat showed less difference than those 

 which were easy to treat. 



GROUPING OF SPECIES. 



GROUPING WITH RESPECT TO PENETRATIONS AND ABSORPTIONS. 



Table 2 (see Appendix) gives the average longitudinal and radial 

 penetrations obtained in the penetrance tests, and the average ab- 

 sorptions of the specimens treated in the cylinder. In this table 

 and in the diagram, figure 3, the species are arranged in order of 

 increasing absorptions in the impregnation test. In figure 3 are also 

 shown the corresponding average longitudinal and radial penetra- 

 tions. While the longitudinal penetrations show a general tendency 

 to increase as the absorptions increase, there is nevertheless a con- 

 siderable variation. The radial penetrations were very small in 

 most of the woods treated and do not seem to bear an important 

 relation to the absorptions. In some cases it is possible that the 

 longitudinal penetrations would have shown a closer relation to the 

 absorptions if the average had been based on the same number of 

 specimens in both series of tests. The penetrations represent the 



