80 



ANNUAL OF SCIENTIFIC DISCOVERY. 



EXPERIMENTS ON THE STRENGTH OF SEVERAL KINDS OF 



BUILDING STONES. 



The following paper, showing the results of experiments on the strength 

 of various kinds of building stones in common use, was recently read before 

 the American Institute of Architects, 1ST. Y., by Mr. R. G. Hatfield. The pres- 

 sure applied was by means of a hydraulic press. The press was constructed 

 for me by Messrs. R. Hoe & Co., in their best style of workmanship; oil, in- 

 stead of water, is used to avoid corrosion, and consequent friction. The pres- 

 sure is indicated at all stages of the experiment by an index moving over a 

 scale on a circular arc the index being operated by levers on knife-edge 

 bearings ; one of these levers is pressed by a piston playing in a small cylin- 

 der, the piston being operated by the oil under pressure. The press has a 

 capacity of 60,000 pounds. 



The Resistance to Crushing. The specimens submitted to this test were 

 two-inch cubes of freestone. They were dressed to the shape about as accu- 

 rately as cut-stone used in the erection of buildings. To prevent any unequal 

 pressure on the parts, they were bedded above and below in a thin layer of 

 fine white sand. The results given below are the pounds per square inch of 

 the surface pressed, required to produce the first fracture. 



Resistance to Cross Strain. The specimens submitted to this test were 

 about 4 X5 inches, and sixteen inches long; laid on chairs, with a clear bear- 

 ing of one foot in length. The figures given below are the reduced results, 

 and exhibit for each kind the constant, s, in the formula l ~ = s, or the 

 weight required to break a piece of the material one inch square, and one 

 foot long, clear bearing, the weight concentrated at the middle of the length. 



