168 



BULLETIN 12, UNITED STATES NATIONAL MUSEUM. 



The average increments of the first series are the average decre- 

 ments of tbe second series as shown in table. As 20,000 ponnds is 

 the highest stress common to all the specimens it will now be used as 

 standard. 



Description. 



Elastic stress. 



Uitiniate stress. 



Large Small 



(series (series 



F'). F'). 



Unannealed : 



li 



14 



If 



U 



If 



Mean . . 

 Annealed : 



24 



21 



2f 



-a------ ■ • 



2S 



Mean . . 



Ponnds. 

 53, 300 

 37, 900 

 29, 500 

 31, 100 

 28, 000 



Pounds. 

 50, 500 

 35, 400 

 29, 300 

 30, 800 

 28, 300 



35,960 34,860 



35, 500 

 33, 800 

 28, 900 

 27, 800 

 25, 500 



33, 200 

 30, 500 

 28, 100 

 27, 900 

 25, 700 



30, 300 29, 080 



Long 



(series 



D). 



Mean. 



30,700 I 33,840 



26, 700 

 29, 800 

 25, 900 



27, 300 

 25, 200 



26, 980 



31, 800 

 31, 367 

 27, 633 

 27, 667 

 25, 467 



28, 787 



Large 

 (series 



Pounds. 

 74, 915 



60, 480 

 51, 456 

 55, 803 

 52, 924 



59, 116 



Small 



(series 



F'). 



Pounds. 

 71, 940 

 56, 740 

 50,345 

 54, 425 

 52, 475 



57, 185 



57, 485 

 54,543 

 51, 076 

 51,338 

 50, 432 



55, 459 

 52, 715 

 50, 350 

 50, 842 

 50, 025 



52,975 ! 51,878 



Long 



(series 



D). 



Potmds. 

 55, 135 

 54, 140 



48, 925 

 50, 160 



49, 280 



51, 528 



45, 460 

 49, 605 



46, 740 

 49, 490 



47, 455 



47, 750 



^lean. 



55, 943 



52, 801 

 52, 288 

 49, 389 

 50, 557 



49, 304 



50, 868 



The large specimens give somewhat higher results than the small, 

 whilst the long ones are very considerably less. 



Series F. 



To ascertain the mechanical effects and the variations caused by dif- 

 ference in the shape and proportion of specimens, rolled steel plates of 

 various thicknesses, tested under pulling stress, the same material as 

 series D, were tested. 



The larger specimens were 10 by 10 inches ; the smaller specimens 

 were 4^ by 1^ inches. In order to develop the change in the form of 

 the large specimens when nnder stress, some of the plates had circles, 

 and others diagonal lines drawn on the surface. The altered appear- 

 ance of these circles and lines at the conclusion of the experiment is 

 shown by a plate. 



It is interesting to compare the result obtained by testing the large 



