PHYSICAL TESTS OF BUILDING STONES 355 



Tests of compressive and tensile strength were not made 

 of these specimens, inasmuch as data of this kind are to bq 

 had in the case of nearly all of the varieties of stone in this 

 series. Besides, the importance of such tests of strength has 

 been overestimated. All of the better quarry stone of the 

 state is strong enough for the ordinary construction, as wall 

 work. Only in exceptional cases is greater strength 

 requisite, as in large arches where the thrust is severe, 

 and in columns and piers supporting a great weight.^"" 



As has been well said, " the problem is not what will a 

 selected and carefully prepared sample of the stone bear to- 

 day, but what will it bear after many seasons' exposure to 

 heat and frost. For all ordinary purposes of construction 

 the excess of strength of any stone over 15,000 pounds per 

 square inch is of little value excepting so far as it denotes 

 density, and hence greater resistance to atmospheric in- 

 fluences." f 



* The compression in the Washington monument, a column 600 feet in height, 



is i8y°q^^ tons per square foot ^ whereas the strength of the marble nsed, is 517 tons, or less 

 than the resistance of the weaker stones. Julien, U. S. Tenth Census, tenth volume, 



P- 359- 



f George P. Merrill, hand-book and catalogue of collection of building and orna- 

 mental stones, in the United States National museum. Rep. Smithsonian institution, 

 1885-86, part II, page 490. 



