Page:Great Neapolitan Earthquake of 1857.djvu/199

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TABLE OF FACTORS FOR COEFFICIENT.

151

The use of the coefficient $\mathrm {L}$ , in Eq. XXI. et seq., considers the value of $l$ (Eq. ${\mathfrak {A}}$ ) evanescent, so that the prism at the moment of fracture has not risen through an appreciable angle, at the surface of fracture, and from the extremely small extensibility of mortar, stones, &c., this is sufficiently true to nature.

Table I.

Factors for the coefficient $\scriptstyle {\mathrm {L} }$ .

Material	1. Weight in pounds per cub. foot Sp. gr.	2. Pounds per square inch Resistance to Pressure.	3. Pounds per square inch Resistance to Tension.	3. Authority for 1 and 2.
Limestone, Caserta, Naples	170	8173	908	Rondelet
Upper Limestone, Geneva	169	4917	546	Gauthey
Jurassic Limestone, Givry	148	4232	496	..
Cretaceous Limestone (Compeigne)	154	3007	334	Rondelet
Lava, Hard Vesuvian	166	8735	972	..
Lava, Soft Vesuvian	107	2209	246	..
Lava, Piperno (Pozzuoli)	162	8140	905	..
Travertino, Old Roman	147	2297	255	..
Travertino, Pæstum	141	3102	345	..
Peperino, Roman	123	3135	347	..
Tufa, Old Roman	78	797	89	..
Tufa, Naples	82	718	80	..
Hard brick	98	1851	206	..
Soft ill-burnt brick	91	1200	133	..
Mortar, lime, and sand, unground	102	423	47	..
Ditto, ditto, ground	119	577	64	..
Mortar, Pozzolano, of Rome and Naples, unground	92	503	56	..
Ditto, ditto, ground	105	732	81	..
Mortar, Old Roman (Campagna)	97	1047	105	..
Mortar, Old French (Bastile)	94	753	84	..
Plaster of Paris (mean)	..	500	55	Laisne

It appears, from the few experiments that have been made, that the resistance of stones, &c., to tension, varies from ${\tfrac {1}{8}}$ th to ${\tfrac {1}{10}}$ th the resistance of the same material to

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