85 



Table 55 Concluded. 



Kind of Wood. 



Two commodities included in the above table deserve special mention and 

 to show the kinds of wood used in making them, separate statistics have been 

 arranged and are presented in the supplemental tables, 55a, mine rollers, 

 and 55b, sprags. 



MINE ROLLERS. 



Table 55a shows seven woods going into slope rollers. They aggregate 

 nearly 2,500,000 feet of material used annually, but this does not represent 

 wood for rollers that are manufactured elsewhere and brought to the State 

 ready for use. Slope mining in recent years is being superseded by the shaft 

 method and with the change is a corresponding decline in the demand for 

 rollers or pulleys used on the slope to prevent abrasion of the cable against 

 the ground. Two-thirds of the roller material is black gum. That obtained 

 from timber cut in the State is mostly the species, Nyssa sylvatica, but that 

 coming from a distance, usually in the form of bolts, is a mixture of the 

 above named species with water gum (Nyssa biflora) , and a small amount 

 probably of tupelo (Nyssa aquatica). Black gum is frequently the common 

 name for all three. The first two species are the most desirable for rollers 

 because of their interlaced fiber that will not splinter nor roughen but wears 

 smooth to a polish by use. Further than this, the woods possess the superior 

 qualities of hardness and toughness, and on account of their abundance, 

 especially in the southern states, are the lowest priced hardwoods. Maple is 

 especially adapted for slope rollers, but owing to its growing scarcity and 

 high price black gum has largely superseded it. Formerly maple was the 

 most used wood for the purpose, but the table shows that the demand for it 

 at present is only one-sixth of that of black gum. 



Veneer cores, the symmetrically round pieces left after the veneer has been 

 removed by the rotary cut process, are now being used for making mine 

 rollers, when the species is one of the black gums. These cores are an off- 



