874 Mr. H, Carrington on Young's Modulus 



^zx, <?xz, <?xy, and a yx denote Poisson's Ratio where 

 lat. strain in the direction ZOZ 

 vz ' long, strain in the direction YOY* 



The following six types o£ experiments were performed: — 

 Tj pe 1. Length in direction XOX, breadth in direction 



YOY, thickness in direction ZOZ, giving values of E# 



and vxy. 

 Type 2. Length in direction XOX, breadth in direction 



ZOZ, thickness in direction YOY, giving values of E# 



and a xz . 

 Type 3. Length in direction YOY, breadth in direction 



XOX, thickness in direction ZOZ, giving values of E y 



and (Tyx- 

 Type 4. Length in direction YOY, breadth in direction 



ZOZ, thickness in direction XOX, giving values of Ey 



and <j yz . 

 Type 5. Length in direction ZOZ, breadth in direction 



XOX, thickness in direction YOY r , giving values of E^ 



and (T Z x< 

 Type 6. Length in direction ZOZ, breadth in direction 



YOY, thickness in direction XOX, giving values of E z 



and G zy . 



In addition to the constants, the elastic limits, and moduli 

 of rupture, the following properties were measured for each 

 test piece : — The density when tested, density dry, humidity, 

 shrinkages in directions XOX and YOY, and the number of 

 annual rings per inch. Each piece was dried immediately 

 after testing in an electrically heated oven at 104 degrees 

 centigrade for from 24 to 48 hours, and then carefully 

 weighed and measured. This enabled the humidity, 

 shrinkages, and dry densities to be obtained. The humidity 

 and shrinkages were calculated as percentages on the weights 

 and dimensions respectively of the dry test pieces, the 

 humidity being taken as 



Weight when tested — Weight when dry 

 Weight when dry 



All the results are tabulated in Table I. 



It will be noted that about 10 experiments of each type 

 were performed for each balk, and that the means of the 

 results are tabulated. Also columns are included showing 

 the probable variation from the mean of each property. 



