444 
Proceedings of the Royal Society of Edinburgh. [Sess. 
50 to 200 per cent, for stones, bricks, and concrete. These figures, except 
the first, may apply almost equally well to the crushing strength, but 
they require experimental support. The corresponding inclinations of the 
surfaces of shearing are 37° for wrought iron and steel, 36° for cast iron, 
and 27° to 15° for stones, etc. The first value is seldom obtained, but the 
others agree fairly well with average experimental results. 
When the crushing plates are of material softer than that under test, 
the lateral flow of the former diminishes the apparent strength of the 
specimen. With stones crushed between lead plates the strength is 
calculated as 035 to 0T5 of that obtained when iron or steel plates are 
employed. Experiments give 065 to 043 as the value of this ratio, but the 
specimens do not rupture by shearing in the manner contemplated. 
The total crushing load of a short specimen of cast iron is increased by 
diminishing the length of the piece, but the crushing stress per unit of area 
is simultaneously decreased. 
REFERENCES. 
(1) Gulliver, Proc. Roy. Soc. Edin ., vol. xxviii., 1908, p. 374. 
(2) Ibid., p. 378. 
(3) Kick, Proc. Inst. Civ. Eng., vol. 1. 1877, p. 188. 
(4) Unwin, Testing of Materials of Construction (Longmans, 1899), p. 393. 
(5) Pace, Atti Coll. Ingeg. Archi., Palermo, 1880, iv. 
(6) Unwin, Brit. Assoc. Report, 1887, p. 879. 
(7) Beare, Proc. Inst. Civ. Eng., vol. cvii., 1891, sect. ii. p. 341. 
(8) Pace, Int. Assoc. Test. Materials, Brussels Congress, 1906, Paper B 10c, p. 7. 
(9) Bauschinger, Mitt. Tech. Hoch., Miinchen, 1876, vi. 
(10) See (4), p. 259. 
The values of y used throughout the paper are taken chiefly from Trautwine, 
Civil Engineer's Pocket-Book (Wiley, New York, 1900), p. 373. 
(. Issued separately July 16 , 1909 .) 
