344 KEPORT ON NATIONAL MUSEUM, 188G. 



form of seams which are parallel to the lines of bedding or distributed 

 in short, interrupted lamina;. These seams, whether continuous or 

 otherwise, are fatal to the integrity of the stone, aud there is scarcely 

 a limestone structure in the country, of twenty-five years standing, 

 which is not more or less dilapidated or unsightly, from the effects of 

 absorption of water by the clay seams, aud the alternate freezing and 

 thawing. When laid in the position of the original beds, which is the 

 usual mode, the separation by the clay seam is slower; bat when used 

 as posts or pillars, with the lines of bedding vertical, the change goes 

 on more rapidly." 



Sandstones, on accouut of their widely varying textures and degrees 

 of compactness, together with an equal variation in composition aud 

 character of cemeuvtiug materials, are influeuced, to a greater or less 

 extent, by all the atmospheric intluences enumerated, hi the order of 

 its apparent importance may be mentiond first tlie eifects of freezing. 

 As will be noticed by reference to the tables in the appendix, sand- 

 stones will absorb from about oue-fiftieth to one-eighth of their weight 

 in water in twenty-four hours, or from 13 per cent, to VJ^S per cent. The 

 approximate amount which a stone may absorb with imi)unity cannot, 

 of course, be stated, since much depends on its i)Osition in a building 

 and the strength and structure of tlie stone itself. It is not too much 

 to say, however, that any stone which will absorb 10 per cent, of its 

 weight of water during twenty-four liours should be looked upon with 

 suspicion until, by actual experiment, it had shown itself capable of 

 withstanding without harm freezing when in this condition. Half of 

 this amount may be considered as too large when tlie stone contains 

 any appreciable amount of calcareous or clayey matter. (See foot-note, 

 p. 348.) 



It is to their great absorptive power that is due the large amount of 

 disintegration and exfoliation seen in the softer sandstones, as the Tri- 

 assic of the Eastern United States and the sub-Carboniferous of Ohio. 

 When a stratified rock, and especially one that is distinctly laminated, is 

 I)laced on edge the water filters into it from above, and, there freezing, 

 from necessity produces the scaling so often noted in the Connecticut 

 brownstone. If placed on the bed the effect is not nearly as disastrous, 

 but with a porous stone the effect of continual freezing and thawing can 

 but be injurious. It was with an apparent eutire disregard of the prob- 

 ble effect of these agencies that was selected the soft and i)orons Jnro- 

 Cretaceous sandstone from Acquia Creek, Virginia, for the constiiiction 

 of the White House, central part of the Capitol, and other ])nl)lie and 

 private buildings in Washington, a stone so susceptible to these inilii- 

 ences, that it is only by a most prodigal use of paint and putty that the 

 buildings are kept in a condition at all presentable.* 



* other reasons than that of lack of durability can be given against the nse of 

 a too porons stone in a house wall. "A red saiidatone house may bo a very handsome 

 building, hut then it may l)o lioldingtons of water, .ind such a wall, if exposed to the 

 northwest, in au open country, in our neighborhood, in a rainy winter, would, no 



