334 



REPORT ON NATIONAL MUSEUM, 1886. 



Ibrtunately tbis can uot at all times of the year aud in all places be 

 (lone, and artificial methods must be resorted to. Brard's process, as 

 modified by M. Hericart and Tlinry, consisted in boiling the cube to be 

 experimented upon for half an hour in a saturated solution of sulphate 

 of soda (Glauber salt) and then allowing it to dry, when tlie salt taken 

 into the pores crystallized aud expanded.in a manner supposedly some- 

 what similar to that of water when freezing.* 



This process is not now in general use, as experiment has shown that 

 the salt exercised a chemical as well as mechanical action, and jHoduces 

 results somewhat at variance with that of freezing water. The most 

 important series of experiments ever performed with the process in 

 this country were those of Mr. C. G. Page, made with reference to the 

 selection of material for the Smithsonian Institution Building at Wash- 

 ington. 



The results are given in the following tablet 



Materials. 



Marbli\ close-drained, Maryland 



Marble, coarse " alum stone," Baltimore Coimty, Md 



Marble, blue, Maryland 



Saiidstoue coarse, "Portland. Conn 



Sandstone, tine, Portland, Conn 



Sandstone, red. Seneca Cieek, Md 



Sauilstone, dove-c<d(i!ed, Seneca Creek, Md 



Sandstone, Little Falls. N. J 



Sandstone, Liltle Fall.s, IST. J 



Sandstone, coarse, Nova Scotia 



Sandstone, d;irk, coarse, Seneca Aqueduct, I'cters's quarry. 



Sandstone, Acquia Creek, Va 



Sandstone, 4 miles above Peters's quarry, Md 



Sandstone, Beaver Bam quarry, Md 



Granite, Port Deposit, Md 



Marble, close-grained, Montsomery County, I'a 



Limestone, blue, Moutsomei-y County, Pa 



Granite, Great Falls of the Potomac - 



Soft brick '- -■ 



Hard brick 



Marble, coarse- dolomite, M ount Pleasant, N. Y 



Specific 

 gravity. 



.834 

 .857 

 .613 



.583 

 .672 

 .480 



.'482 

 .518 



230 



.609 

 .727 

 .G9SJ 



Loss in 

 grains. 



0.19 

 0.50 

 0.34 



14.36 



24.93 

 0.70 

 1.78 

 1.58 



•0.62 

 2.16 

 5.60 



18.60 

 L58 

 1.72 

 5. 05 

 0.35 

 0.28' 

 0.35 



16.46 

 L07 

 0.91 



The specimens operated ui)on, it sliould be stated, were cut in the form 

 of inch cubes. Each was immersed for half an hour in the boiling 

 solution of sulphate of soda, and then hung up to dry, this perform- 

 ance being repeated daily throughout; the four weeks which the exi)er- 

 iment lasted. 



The injurious effects of artificial heat, such as is produced by a burn- 

 ing building, arc, of course, greater in i)roportion as the temperature is 

 higher. Unfortunately sufficient and reliable data are not at hand for 

 estimating accurately the comparative enduring powers .of various 

 stones under these trying circumstances. It seems, however, to be well 

 proven that of all stones granite is the least fire-proof, while the fact 

 that certain of the fiue-grained siliceous sandstones are used for furnace 



* Chateau, Techuologie Dii Balinieut, Vol. i, p. 2G2. 



tFrom Hints ou Public Arcliitecturo by Robert Dale Owen, p. 119. 



