10. No branch of mason work, from an architectural standpoint, is of greater importance than the selection of stone for structural purposes; and the qualities of stone, such as its strength and durability when exposed to great variations of temperature and action of the weather, its permanence of color, etc., are points to be studied with great care.

11. Strength

Strength. Whenever a stone is to be used for foundations, piers, lintels, bearing blocks, etc., its strength is a matter of importance. If the stone appears to be a first-class one, its strength may be assumed as equal to the average strength of stones of that kind, as determined by experiment.

The cap and bond stones for piers carrying iron columns, and the bearing blocks under the ends of the girders, should be either granite, bluestone, or hard, blue Vermont marble. For use in such situations, the safe bearing strength should not be assumed greater than one-tenth of the crushing strength. The stones in piers, etc. , in warehouses and office buildings, are often subjected to loads of from 60,000 to 70,000 pounds per square foot.

12. Table 1 gives the load per square inch at which the different kinds of stone fail.

Table 1. Crushing Strength Of Stone

KINDS OK STONE.

STRENGTH, LB. PER SQ. IN.

Granites -

Staten Island, blue..............

22,250

Maine.................................................

15,000

Quincy, Mass................

17,750

Richmond, Va.......................................

21,250

Cape Ann, Mass.....................

12,420

19,500

Weterly, R, I................

14,940

Fall River, Mass.................

15,940

Duluth, Minn..............

17,750

Maryland Granite Co..........

19,430

Limestones -

Glens Falls, N. Y...................

11,475

Lake Champion, N.Y............

25,000

Kingston, N.Y.............

20,700

Joliet, 111........................................

16,900

Lime Island, Mich................

23,800

18,000

Bardstown, Ky............

16,250

Cooper Co, Mo..............

6,650

North River bluestone...........

19,820

Marbles -

East Chester, N. Y..................

13,500

Italian, Common..............

13,060

Dorset, Vt..........................

7,610

Procors, Vt., blue.................

14,410

Lee, Mass., white..............

13,440

Mill Creek, 111., drab................

9,700

North Bay, Wis., drab..............

20,000

KINDS OF STONE.

STRENGTH, LB. PER SQ. IN.

Sandstones -

Little Falls, N. Y., brown............

9,850

Belleville, N. J., gray and red........

11,700

Middletown, Conn., brown...........

6,950

Haverstraw, N. Y., red..............

4,350

Medina, N.Y. pink................

17,700

Berea, O., drab......................

7,250

10,250

Vermilion, O., drab..................

8,850

Marquette, Mich., gray...............

7,450

Seneca, O., red brown...............

9,700

Cleveland, O., olive green............

6,800

Albion, N. Y., brown................

13,500

Kasota, Minn., pink..................

10,700

Frontenac, Minn., light buff..........

6,250

Dorchester, N. B., freestone..........

9,150

Massillon, O., yellow drab..................

8,750

Warrensburg, Mo., blue drab.............

5,000