320 [Assembly 



X. 



Results of the Trials of the Strength of some or the Speci- 

 mens submitted TO the Capitol Commissioners, made at Wash- 

 ington IN November, 1868. 



Specimens of the gray gneiss of Saratoga county of one inch cubes 

 placed between steel plates, sustained a pressure of from 16,800 ta 

 25,600 pounds ; the lowest number doubtless from imperfection. The 

 average of these specimens gave 22,666 pounds as the crushing weight 

 per square inch. 



Of the dark colored sienite, the range was from 18,000 to 25,700 

 pounds as the crushing weight; the lowest number in this case result- 

 ing from the want of entire parallelism in the two fases of the cube. 

 The average of four specimens gives 22,575 pounds as the crushing 

 weight per square inch. 



A single cube of one and a half inches, from one of the beds of 

 Tribes Hill limestone, sustained a pressure of 66,300 pounds, or 

 25,022 pounds to the square inch, before breaking. A similar speci- 

 men from another layer of the same limestone, sustained a pressure of 

 54,400 pounds, or 24,622 pounds to the square inch. 



Three specimens of limestone from the Cobleskill quarries, in 

 blocks of one and a half inch cubes, gave a range of from 51,000 ta 

 72,700 pounds of pressure before breaking, being an average of 27,407 

 pounds to the square inch. A single cube of one and a half inches 

 from another bed of the same limestone, gave 21,066 pounds as the 

 crushing weight, to the square inch. 



Three specimens of compact white marble from Alford, Mass., in 

 one and a half inch cubes, sustained respectively 26,300, 26,900 and 

 27j000 pounds before breaking, giving very nearly 12,000 pounds as 

 the crushing weight, per square inch. 



These experiments sustain the opinion previously expressed in my 

 report, that these compact limestones are stronger than the marbles, 

 and equal to many of the granites. 



In regard to the lateral strength of these stones, we have a right to 

 infer from the close grain and compact texture, as well as tenacity 

 shown in the process of crushing, that they are also superior in that 

 character. 



I may remark in this place, that the stone used in the New Capitol 

 foundation at Washington, is gneissoid rock or mica slate, and has 

 not the strength of the gneiss and limestones here recorded. 



The remaining collection of specimens submitted for trial have been 

 left with Prof. Joseph Henry, and the results of the experiments 

 will be reported at a future time. 



Very respectfully. 



Your obedient servant, 



JAMES HALL. 



Note. — The remarks upon the red or brown sandstone (freestone), 

 arcMuainly based upon an experience of the Connecticut river stone 

 and in a smaller degree upon that from !New Jersey. The sandstone of 

 the same age on the Potomac river, in Maryland, known as the Seneca 



