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SECOND TABLE OF FACTORS.

compression. The third column is here calculated on the mean of such data. It cannot be viewed as more than an approximation, except in the cases of mortars, which are from actual experiment, as given by Gauthey ('Sur la Construction des Ponts'), and by Rondelet ('L'Art de Bâtir').

Table II.

Of the specific gravities, cohesion, and mutual adhesion, of various building materials. Factors for the coefficient $\scriptstyle {\mathrm {L} }$ .

Material	1. Weight in pounds per cub. foot Specific gravity	2. Resistance to Tension lbs. per square inch.	3. Adherent Resistance lbs. per square inch.	3. Authority.
Granite	164	1200?	..	T.
Granite to Portland cement	..	..	97	W.
Granite to Parker's cement	..	..	22	W.
Silurian slate	170	2300?	..	T.
Oolite (Portland)	132	270	..	W.
Oolite to Portland cement	..	..	146	W.
Oolite to Parker's cement	..	..	42	W.
Sandstone, coal measure	147	234 to 250	..	T.
Millstone grit and Portland cement	..	..	76	W.
Sandstone (Whitby) and Portland cement	..	..	57	W.
Kentish rag and Parker's cement	..	..	29	W.
Brick, best English	135	200 to 230	..	..
Brick, inferior	97	40 to 80	..	B.
English brick in Portland cement	107	..	..	W.
Portland cement	127	400	..	W.
Parker's cement	120	300	..	W.
Mortar (sand 3, lime 1)	100 to 119	11 to 20	9.88	B.G.
Green and fresh	..	2	..	T. T.
Mortar, ground lime and tiles	100 to 120	40 to 80	5.26	B. G.
Hydraulic mortar	100 to 120	40 to 80	5.26	T. T.
Jurassic limestone to mortar	..	..	3.80	R.
Brick and tile to mortar	..	..	8.27	R.

Authorities.—T., Tredgold. W., White, 'Trans. Inst. C. E.' B., Barlow. B.G., Boistard and Ganthey, 'Const. des Ponts.' T. T., Treussart and Totten. R., Rondelet.

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