— 46 — 



^=-&d <2) 



where w=maximum load at the center of the beam in lbs. 



b, h, l=breadth, height, and span of the beam, in inches. 



d= deflection produced by the load given in inches within the elastic 

 limit. 



p=load at a point in the beam within the elastic limit, correspond- 

 ing to d given in lbs. 



f= Modulus of rupture, pounds per square inch. 



E=modulus of elasticity, pounds per square inch. 

 In fact, within the limit of elasticity, diagram showing the resulting stress 

 and strain is a straight line according to Hooke's law. Beyond that limit, 

 the deflection increases suddenly out of proportion to the load, forming a 

 curve. The modulus of elasticity (E) is obtainable from formula (2) by 

 applying load (p) and corresponding deflection (d). By computing from 

 formula (1) f at the moment of rupture is obtainable. The amount of 

 work done denoted by (A) upon the beam is read graphically by means 

 of a planimetre on the diagram. 



3. Deteemination of Weight. 



With the purpose of determining the relation of the strength of wood 

 to its weight, the weight was taken immediately after testing. The weight 

 so obtained will furnish the weight of the wood per cubic ft. 



4. Drying and Steaming. 



For the drying the wood was put into a drying chamber; for the 

 steaming wood it was put into a steaming room closed with a well-fitted 

 lid. After steaming the wood for 9 hours it was taken out and was 

 introduced into drying chamber where warm air was passed over it at a 

 temperature from 35° to 43°C. by artificial means and after two weeks the 

 wood was fully dried. 



5. Determination of Moisture Content, 



With the object of studying the relation between the moisture content 

 of wood and the strength of wood, one-inch section was cut off from one 

 end of the tested beam used for cross-breaking after the termination of 



