348 REPORT ON NATIONAL MUSEUM, 188(5. 



of rotten rock that bad accumulated during^ previous geologic ages 

 has beeu eutirely removed, if the surface of the rock as displayed 

 in the quarry or natural outcrops presents a fresh and undecom- 

 posed appearance, this may be construed as a strong argument in its 

 favor, though it can not in all cases be accepted as conclusive.* A 

 purely calcareous rock may weather rapidly and yet leave no debri.s, 

 since its constituents are soluble and may all be carried away by 

 running water, leaving no traces to tell of the havoc going steadily on. 

 Impure limestones and all silicious rocks, however, leave more or less 

 debris as mark of their decay. 



But in regions south, of the glaciated area the rock is still covered by 

 the decomposed mass, and hence no clew can thus be obtained. In 

 such cases one can only have recourse to structures tiiat have alreiidy 

 been erected from the stone in question and there observe its weather- 

 ing qualities, or, if these are lacking, observe tlie stone in tho.se pans 

 of the quarry that have not recently been worked. In o[)ening a new 

 (|uarTy, blocks should always be tested by allowing them to lie and sea- 

 son for at least a year before using. At the end of this time the pres- 

 ence of any readily oxidizable pj'rite will have made its presence known, 

 and the amount of disintegration, or induration, as the case may be, 

 wdl furnislx a slight clew regarding its future behavior. Indeed, this 

 seasoning of stone prior to its introduction into a building should always 

 be insisted upon, whatever its character. A good biiilding stone, 

 whatever its kind, should possess a moderately tine and even texture, 

 with the grains w^ell comi>acted, should give out a clear ringing sound 

 when struck with a hammer t and show always a clean fresh fracture. 

 It should also be capable of absorbing only a proportionally small 

 amount of water. | 



iicross New Jersey; thence northwesterly across Pennsylvania into New York State 

 soutli of Buft'alo; thence southwesterly to near central Ohio; thence dne south 

 nearly to the Ohio River; westerly along the river to a point north of Louisville, 

 Ky. ; thence northerly again nearly to Indianapolis, lud. ; thence southwesterly so as 

 to include nearly all of Illinois; thence northwesterly to a point near Saint Louis; 

 ■westerly toward Jefferson City, Mo.; thence along the Osage River and northwesi- 

 erly through Kansas near Topcka; through the eastern half of Nehraska, tlirougli 

 Dakota west of Bismark, and thence onward into Montana. 



* "No artificial structure or position will ever subject the stone to the same degree 

 of weathering influence to which it is exposed in its natural position. * * * 'i'lie. 

 rock which has withstood these inlluences is quite equal to witlistand tlie exposure ol' 

 a few centuries in an artificial structure. " (Hall Rep. on Building Stone, ]». -21.) 



t In a report on some experiments on the transverse strength and elasticity of liuild- 

 ing stone, Mr. T. II. Johnson states " the resonance of each piece tested was propor- 

 tional to the modulus of elasticity as found by the test." (Kep. State Geol. of Iiid., 

 1881, p. 38.) 



t En uu mot, les qualites essentiolles des pierres tantdures quo tendres sont d'avoir 

 le grain fin et homogfeno, la texture uuiforme et compacte ; de ril^ister a I'humidite 

 a la geloe, et de ne j)as clater aii feu en cas d'incendie. (Chateau, Vol. i, p. 272.) 



Any sandstone weighing less tlian 130 pounds per cubic foot, absorbing more than 

 Jjper cent, of its weight of water in twenty- four hours, and effervescing anything but 

 feebly with acids, is liable to prove a second-class stosio as regards durability where 

 there is frost or much acid in the air." (Notes on Building Construction, p. 36.) 



