8 



botli the large beam machine and the 100,000-i>oiincl universal machine. The hiads are weighed 

 on this latter machine the same as for the beam tests. Tlie plunger in the column machine 

 hasjust ten times the area of that in the weighing machine, and hence the loads in the column 

 tests are just ten times those indicated on the weighing beam. The tail block is of cast iron, rest 

 iug in a spherical socket, which is carried on a.car and which can be held by struts resting in slots 

 in the timber. The outer ends of these struts are kejit from spreading by means of tiebars, as 

 shown, and the whole combination can be moved forward or back, so as to malvc the distance be- 

 tween face plates any even number of feet from two to thirty-six. The spherical s i.-kct in the tail 

 block will produce an accurate adjustment of the end bearings at the beginning of the test, but 

 after the load is on it is thought tluvt this joint will remain rigid, the same as a solid block, espe- 

 cially if precautious are taken to increase the frictional resistance between these bearing surfaces. 

 This spherical socket is provided to eliminate the effects of unequal shrinkage in the side timbers 

 or any unequal comjnession in the bearing sockets, and not to serve as a round-end bearing for 

 tlie column. VVlien long columns are testetl a part of their weight will be supported by means of 

 lines and ])ulleys, so as to make the test correspond to a vertical load in actual practice, ^^o tests 

 of (lolnmns on long-leaf yellow pine have been made <ni this machine at the time of the publication 

 of this bulletin. 



iSifinificance of results. ^ 



From the cross-breaking tests are obtained the cross-breaking modulus of rupture, the modulus 

 of strength at the elastic limit, the modulus of elasticity, or measure of the stiflhess, and the elas- 

 tic resilience, or measure of the toughness. 



The loads and their corresponding deflections are plotted as rectangular coordinates, and the 

 strength at the elastic limit, the modulus of elasticity, and the elastic resilience are obtained from 

 a study of this strain diagram. 



The following is an example of the record made for every beam test. This is a record of a test 

 made on a 4 x 8 inch stick of long-leaf pine, 12 feet long, which was placed on supports 140 inches 

 ajjurt. 



CROSS-BREAKING TEST. 



^P 



Mark <3 



h 



Length, 140.0 inches. 

 Height, S.Ot inches. 

 Breadth, 4.02 inches. 



Modiihis of Ruptures, 

 3W1 



wh(Te /' ^= =10,910 ponnds i>er square inch. 



2 /( /- - 

 Modulus of Strength at the Elastic 

 3W'l 



Liniit=/= =»><,100 pounds per sciunn- inch. 



2b h- 

 Modulus of Elasticity =2,070,000 pouuds ]ier sipiarc inch. 

 Total Resilienee = 3."i,410 inch pounds. 

 Resilience, p(^r cub. iuch = 7.83 incli-i>onnds. 

 Total Elastic Resilience =8,050 iuch-)>ound8. 

 Elastic Resilience, per cubic inch = 1.91 iuch-pouu^l3. 



(Number of annu.il rJDgs per inch= 14.) 



Remarks. 



Bntt vm\. 



Maximum load. 



The observed data are given in the columns headed "Time," " Load," and "Scale reading." 

 These results are recorded on this sheet in ink as they are observed. The result in the " Detlec- 



