184 THE GEOLOGY OF MINNESOTA. 



[Qualitative tests. 



(B.) GENERAL TABLE OF QUALITATIVE TESTS OF MINNESOTA 

 BUILDING STONES. 



For the purpose of reaching results that would serve as a basis for com- 

 paring the building-stones of Minnesota with each other, and with those 

 from other states, average samples were obtained and subjected to such 

 physical tests as could be devised that would represent the intensified nat- 

 ural action of the weather. These physical tests were performed by Prof. 

 J. A. Dodge of the University of Minnesota, and the chemical analyses of 

 the same stones were also done by him, or under his direction by Mr. C. F. 

 Sidener. At the same time duplicate two-inch cubes were subjected to 

 pressure at Fort Wadsworth, Staten Island, under the direction of Gen. Q. 

 A. Gillmore, one cube being crushed in the direction of the bedding, and 

 the other in a direction across it, between steel plates. The results of these 

 tests are brought together for comparison in the Systematic table of the qual- 

 ities of Minnesota building stones, already referred to. 



In the same table these results are carried out into mathematical 

 expressions, by a series of credits on a scale of ten, the final results being 

 placed on a scale of rank from 100 downward, so that each stone stands in 

 the final result wherever the sum of its credits may warrant. In getting 

 these credits of the individual stones, in each case the highest attained 

 result has been taken as 10 and the lowest as 1. The intermediate results 

 have been distributed proportionately between 10 and 1. In those cases 

 where the first results, are not expressed by figures, an estimate has been made 

 and expressed in figures, the highest rank (10) being given to those stones 

 that stood the test in question most successfully. This comparison is made 

 on the assumption that all the tests included in the credit columns are of 

 equal value in indicating the comparative worth of the stones, but in reality 

 some are of much more value than others. It is evident that specific 

 gravity may be reckoned either a favorable or unfavorable element. In 

 some situations, or for some uses, it is desirable to have a light stone, and 

 in others a heavy one. The same is true in regard to some of the other 

 qualities. Those elements, in general, which go to make up a very durable 

 building-stone, and thus act affirmatively for the stone as a part of the 

 structure, also go to make it incorrigible in the builder's hands, and to that 

 extent act negatively. For these reasons specific gravity has not been 



