Part IV, 



Appendix A. 



THE QUALITIES OF BUILDING STONE AS SHOWN BY THEIR CRUSHING 

 STRENGTH, WEIGHT, RATIO OF ABSORPTION, AND CHEMICAL COM- 

 POSITION. 



(1) GENERAL REMARKS. 



The present methods of testing building stone are at best extremely 

 unsatisfactory and the results obtained unreliable. In the majority of 

 cases, indeed, no attempt is made to ascertain the resistance of the 

 material to the action of fire, frost, or the general effects of weathering. 

 This is due in part (1) to a lack of knowledge of methods by which such 

 tests can be made, (2) to a lack of appreciation of the necessity of such 

 tests, (3) to a desire on the part of quarriers to get the stone immediately 

 upon the market without the delay necessitated by a long series of ex- 

 periments, (4) to the expenses attendant upon such experiments, and 

 (5) in altogether too many cases to a desire on the part of interested 

 parties to sell the stone regardless of its qualities. Even the tests that 

 are now applied are in many cases practically valueless, owing to a lack 

 of definiteness in stating results, or our inability with our present knowl- 

 edge to interpret them properly. Take for instance the chemical 

 analysis of a sand stone as ordinarily given. This shows the presence 

 of certain percentages of iron oxides, alumina, lime, and silica, but we 

 have no means of knowing in just what conditions these substances ex- 

 ist; whether the iron occurs as a hydrous or anhydrous oxide, is con- 

 fined wholly to the cementing material, or is a constituent of the vari- 

 ous minerals composing the stone itself. The same may be said re- 

 garding at least a part of the silica, alumina, and lime. These diffi- 

 culties may be in part avoided if the analysis is supplemented by a 

 microscopic examination, whereby is ascertained the mineralogical nat- 

 ure of the stone, its structure, and the freedom from decomposition of 

 its constituent parts. And indeed as a rule it may be said that while 

 the analysis of any stone is of interest in a general way, it fails com- 

 pletely to give more than an approximate idea of its value for construct- 

 ive purposes. Any analysis should always be preceded by a micro- 

 scopic examination, and if the results of such examination should show 

 it to be essential this should be followed by a pulverization and me- 



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