Compressive Resistance of Connecticut Brownstone.
To the Editor of Stone:
SIR: In the current technical literature of the architectural profession and the building trades, and in the numerous text and hand-books issued for the use of architects, engineers, contractors and builders, so many varying and misleading tables are printed, setting forth the strength of material, and particularly the resistance to compression of the various building stones, that it is considered important to furnish correct figures regarding the stone quarried in Connecticut, and best known under the commercial term of Connecticut brownstone. I beg leave to transmit herewith a series of tests made upon stone from the Shaler & Hall Quarry Co., and the Middlesex Quarry Co., both of Portland, Conn., and the New England Brownstone Co., of Cromwell, Conn., on various grades, including the coarser qualities, which, however, are not sold as building stone, but for bridges, abutments, piers and railroad work generally. From these tests it will be seen that the average resistance of twenty cubes varying from 1 ½ to 3 inches is 10,956 pounds on all grades, and if the bridge stone is excluded the average of twelve samples of building stone is 12,582 pounds resistance per square inch. Two of these tests were made at the United States Arsenal, Watertown, Mass., and are exact copies of original reports duly certified by Government officials. The tests of the Middlesex Company stone were made by the Colt's Patent Firearms Mfg. Co., of Hartford, Conn., and are equally authoritative and correct. It is absolutely fair and accurate therefore to quote the resistance as somewhat between 10,956 and 12,582, or if building stone alone is contemplated, to quote the latter figures only.
In connection with this subject permit me to suggest that as this stone is so much better known, in fact is almost universally known by its trade or commercial name of Connecticut brownstone, and by that name is specialized or distinguished from the many other varieties of building stone, a separate heading using that term might advantageously be employed in your tabulation; inasmuch as it would be more readily comprehended and understood by the profession, the trades, and by students who desire to consult such work of reference, than the lithological term of Connecticut Sandstone or the stone-cutters designation of Connecticut Freestone.
Report by Colt's Patent Fire Arms Manufacturing Co. of Tests of the Resistance of Portland Stone to Gradually Applied Pressure.
The specimens, four in number, in the form of nearly cubical blocks about 1 ½ inch square, were received April 12th, 1880, from the Middlesex Quarry Company and tested for them.
The pressures were applied through steel plates in contact with those surfaces of the block which were parallel to the natural bed of the stone.
Except in the case of the specimens of grade No. 1, the stone surfaces were not flat and did not present a full bearing to the pressure plates; consequently the full strength of the stones of grades 2, 3 and 4, is not given by these tests.
The results of the tests are give in the following table, in which dimensions are stated in inches, areas in square inches and pressures in resistance in pounds.
In the November issue of "Stone," on page 503, you gave a table of "Crushing Tests of Building Stone," in which the Connecticut stone, under two separate headings is given at resistances very obviously to its disadvantage. Will you please make correction in the December number, and oblige,
Yours, very truly, Frank E. Knight.
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