Adams <& Coker — The Floio of Marble. 483 



employed, but in which the deformation was carried on very 

 slowly, being extended over a period of 30 days, and in which 

 the marble after deformation was allowed to remain in its 

 enclosing steel tube for two years, after which time the steel 

 tube was turned off in the usual way and the marble tested in 

 compression to determine its strength. As will be seen by 

 consulting the table on page 479, under these conditions of 

 slow deformation and long, subsequent rest, the deformed 

 marble is but little weaker than the original rock, its strength 

 being on an average 84*7 per cent of that which it originally 

 possessed, while one of the deformed columns in this series 

 showed a strength greater than the average strength possessed 

 by the columns of the original rock. 



Another series of three experiments, the results of which 

 were published in a former paper, show that slow deformation 

 alone conduces to increase of strength. In these experiments 

 the deformation was carried on in wrought iron tubes, and at 

 the conclusion of the experiments the tubes, instead of being 

 placed in a lathe and turned off from the enclosing marble, 

 were sawn in two vertically and the half columns of marble 

 thus obtained. These when tested in compression gave the 

 following results : 





Original 

 height 



Original 

 diameter 



Crushing load 

 Greatest for deformed 

 diameter Time of marble, 

 after de- deforma- lbs. per 

 formation tion square inch 



Experiment A 



1-594 



1-000 



1 : 407 64 days 5350 







1-594 



1-000 



1-203 \\ hours 4000 



P 



1-505 



1-000 



1-388 10 minutes 2776 



These values cannot be used for comparison with those of the 

 former table owing to the fact that the shapes of the test pieces 

 in the two series of experiments were quite different, but 

 compared with one another we see clearly that slow deforma- 

 tion conduces greatly to the preservation of strength. 



2. Deformation of the dry marble when heated to temperatures 

 of 30d° C. and £00° C. 



In a former paper an account has been given of the defor- 

 mation of the marble at these temperatures. Debray* has shown 

 that calcite when heated in closed vessels to a temperature of 

 350° C. suffers no decomposition, that at 440° C. the decomposi- 

 tion is " insensible," while at 860° C. the disassociation of the 

 molecule of carbonate of lime is marked. In the experiments 

 carried out at 400° C, therefore, it would seem that the marble 

 was deformed at the highest temperature which could be 

 employed without danger of decomposition under atmospheric 

 conditions of pressure. 



* Comptes Eendus, 1867, p. 603. 



