QUARRY MATERIALS OF NEW YORK 47 



McCourt, 1 who experimented with some of the principal building 

 stones from local quarries, employed three-inch cubes, making, so 

 far as the materials would allow, six tests on each sample. Four 

 tests were performed in a Seger gas furnace in which one cube at 

 a time was heated. The heat was applied gradually until a tempera- 

 ture of 550 C. was reached, this being maintained for half an hour. 

 The cube was then taken out and allowed to cool in the air. A 

 second sample was heated to the same temperature and then chilled 

 suddenly by a stream of water. The third tube was treated in the 

 same way as the first, except it was heated to 850 , and the fourth 

 heated to 850 was chilled with water. Five tests were made with 

 a gas blast to imitate, so far as practicable, the actual play of flame 

 in a conflagration. On one sample, the blast operated for ten 

 minutes, enveloping three sides in a steady stream ; after cooling 

 for five minutes, the cube again received the blast during ten min- 

 utes, after which it was cooled. The second cube was subjected to 

 the flame for ten minutes and then a strong stream of water along 

 with the blast for a period of five minutes. Then the water was 

 turned off and the flame continued for another five minutes, after 

 which, for five minutes more, the flame and water together were 

 allowed to act on the sample. For the details for the tests, the 

 reader should consult the paper itself. In brief, the results showed 

 that all stones were fairly resistant to a temperature of 550 C. 

 (1022 F.), and curiously, the granites showed up somewhat better 

 than the others. At 850 C. (1562 F.), which probably represents 

 the degree of heat reached in a conflagration, perhaps exceeding the 

 temperature in some cases, all the stones were more or less injured, 

 the amount of damage varying with the individual cubes. The 

 granites and gneisses cracked and spalled. The sandstones parted 

 along the bedding planes, a few developing cross-fractures. The 

 limestones were little injured up to the point where calcination 

 began, but after that they failed badly. The marbles developed 

 cracks before the calcination temperature. The results, as pointed 

 out by McCourt, were indicative of the effects of flame and 

 water upon exposed stone work like cornices, lintels etc., rather 

 than upon stone laid in walls which would suffer much less injury. 



Action of frost. Structural stone that is exposed to the recurrent 

 effects of freezing and thawing may suffer more or less damage 

 therefrom in the course of time. The ability to resist this kind of 

 weathering is to some extent measurable by porosity, since it is the 



1 Op. cit. 



