74 JOURNAL OF FORESTRY 



Elm, soft maple, hard maple, beech, birch, hickory, red gum, tupelo 

 and Other so-called inferior woods will make good ties if cut during 

 the dormant period, seasoned properly and treated thoroughly. Em- 

 phasis is laid on the necessity of personal supervision of these ties 

 from the woods to the treating point. A lot of 600 hard maple ties cut 

 in winter, seasoned, treated by Card process, and laid in Nebraska in 

 1911 are still in perfect condition, and it is estimated that 90 per cent 

 will give 20 years' life and 50 per cent 25 years. 



Chestnut is said to give no better results treated than untreated, 

 owing to the fact that it soon wears out when used in the main line, 

 the average life being about six years. 



Taking all untreated woods together, birch, beech, chestnut, gum, 

 hemlock, tamarack and others, after 10 years 87.7 had been removed 

 on account of decay and 4.3 per cent for other causes, 



S. J. R. 



Leakage Resistance of Steel Railway Roadbeds and Its Relation to 

 Electrolysis of Underground Structures. By E. R. Shepard. Tech- 

 nologic Paper No. 127, Bu. of Standards, U. S. Dept. Commerce, 

 Washington, D. C, 1919. Pp. 39. 



The object of this paper is to present leakage-resistance data on a 

 number of types of roadbeds for different weather and soil conditions 

 and to discuss the several factors which influence the resistance of 

 roadbeds. Of interest to wood technologists, attention is called to the 

 resistance measurements on treated and untreated wood cross-ties. 



From this series of tests it appears that moisture m excess of 20 

 or 25 per cent has little effect in reducing the electrical resistance of 

 wood, while with less than about 10 per cent of moisture the resistance 

 increases rapidly. Ties embedded in the earth or in paved city streets 

 would probably retain moisture in excess of 20 per cent throughout the 

 year and therefore would not change their resistance materially with 

 seasonal changes. On the other hand, in open construction the mois- 

 ture content, and therefore the resistance, would vary through wide 

 limits. 



For a given moisture content the electrical resistance of chestnut 

 and oak are practically the same, but chestnut wood air dries more 

 rapidly than oak and therefore has a higher resistance for a given time 

 of air seasoning. 



"Zinc chloride and other chemical salts used as preservatives render 

 ties highly conducting and greatly increase leakage currents from 



