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 424 STRENGTH OF MATERIALS possible variations, are readily distinguished. Fig. 9 is white cast iron. Its surface, where fractured, has the general appearance of broken tool steel, but the color and texture of the met- FIG. 9. al are distinctive; it has none of the "steely grain." Fig. 10 represents dark foundery iron. Its color, its granular structure, and coarse grain are markedly characteristic. 33. Good iron plates should, in ad- dition to the above tests, be subjected to the following : When red-hot, they should be capable of being bent sharp- ly to a right angle without cracking, up to an inch in thickness. Ordina- ry boiler plate of good quality should bend double. When cold, they should bend along the grain without cracking, FlG 10 as follows : 1 in. thick, 15 ; in. thick, 25 ; in. thick, 35 ; ^ in. thick, 90. Across the grain they should at least bend half as far. They should be bent on a slab rounded on the corners with a radius of in. Steel plates should be 50 per cent, more ductile. 34. Testing within the Limit of Elasticity. In determining the value of materials of construction, it is usu- ally more necessary to determine the position of the limit of elasticity, and the behavior of the metal within that limit, than to ascertain ultimate strength or resilience. It should be possible to test every piece of material which goes into an important structure, and then to use it with confidence that it has been proved capable of carrying its load with a sufficient and known margin of safety. It is common to test bridge rods to a limit of strain deter- mined by specification, and to compel their re- jection when they are found to take a consid- STRICKLAND erable permanent set under that strain. Spe- cification now frequently (and it should inva- riably) makes the limit of elasticity the basis of calculation and test. See Fairbairn, "Cast and Wrought Iron " (London, 1865) ; Haswell, " Engineers' and Mechanics' Pocket Book " (New York, 1868); Trautwine, "Civil Engi- neers' Pocket Book" (Philadelphia, 1872); Rankine, "Useful Rules and Tables" (Lon- don, 1872); Thurston, "Strength, Elasticity, Ductility, and Resilience of Materials of Con- struction" (Philadelphia, 1874); and Wood, "Resistance of Materials" (New York, 1875). STRICKLAND, Agnes, an English authoress, born at Reydon hall, Suffolk, July 19, 1796, died in London, July 13, 1874. She was care- fully educated under the personal supervision of her father. Her works are: "Worcester Field, or the Cavalier," a poem (1812); "De- metrius," a poetical romance (1833) ; " The Pilgrims of Walsingham," a series of tales (1835); "Alda, the British Captive" (1841); with her sister Elizabeth, " Lives of the Queens of England" (12 vols., 1840-'49; abridged and edited by Caroline G. Parker, 1 vol. 12mo, New York, 1867), and " Lives of the Queens of Scotland" (8 vols., 1850-'59); " Queen Vic- toria, from her Birth to her Bridal " (2 vols., 1840); "Historic Scenes and Poetic Fancies" (1850) ; " Old Friends and New Acquaint- ances" (1850); "Lives of the Bachelor Kings of England" (1861); "How will it End?" a novel (1865); "Lives of the Seven Bishops committed to the Tower in 1688 " (1866) ; and " Lives of the Tudor Princesses " (1868). She edited an edition of the letters of Mary, queen of Scots, and thus brought to public notice many documents of much historic value. In 1871 she received an annual pension of 100. The sisters of Miss Strickland, JANE MAR- GARET, CATHARINE PARR (Mrs. Trail), and SU- SANNAH (Mrs. Moodie), besides assisting her in her historical works, published several books under their own names. Mrs. Trail and Mrs. Moodie are residents of Canada, and their chief works have been upon life in that country. STRICKLAND, William Peter, an American cler- gyman, born in Pittsburgh, Pa., Aug. 17, 1809. He was educated at the Ohio university, Ath- ens, O., entered the ministry of the Metho- dist Episcopal church in 1832, labored sev- eral years in Cincinnati, and then became agent of the American Bible society. In 1850 the Ohio university conferred on him the de- gree of D. D. In 1856 he removed to New York, where he engaged in literary labor, mostly in connection with the Methodist book concern. In 1862 he was chaplain of the 48th New York regiment, stationed at Port Royal, S. C. Since 1866 he has been pastor of the Presbyterian church in Bridgehampton, L. I. His principal publications are: "History of the American Bible Society" (New York, 1849 ; new ed., with history continued, 1856) ; "History of Methodist Missions" (1850); "Genius and Mission of Methodism" (1851);