428 Canadian Record of Science. 



selected for study. The investigation is now being 

 extended to various other limestones, as well as to 

 granites and other rocks. 



In order to submit the marble to a differential 

 pressure, under the conditions above outlined, it was 

 sought to enclose the rock in some metal having a 

 higher elastic limit than marble, and at the same time 

 possessing considerable ductility. After a long series 

 of experiments, heavy wrought-iron tubes of special 

 construction were adopted. These were made, follow- 

 ing the plan adopted in the construction of ordnance, 

 by rolling thin strips of Low Moor iron around a bar 

 of soft iron, and welding the strips successively to the 

 bar, as they were rolled around it. The core of soft 

 iron composing the bar was then bored out, leaving a 

 tube of Low Moor iron, the sides being about i inch 

 in thickness, and so constructed that the fibres of the 

 iron ran around the tube instead of being parallel to 

 its length. These were found to answer the require- 

 ments admirably. 



The following procedure was then adopted. Columns 

 of the marble, an inch or in some cases . 8 inch in 

 diameter and about 1 . 5 inch in length, were accu- 

 rately turned and polished. The tube was then very 

 accurately fitted around the marble. This was accom- 

 plished by giving a very slight taper to both the 

 column and the interior of the tube, and so arranging 

 it that the marble would only pass half way into the 

 tube when cold. The tube was then expanded by 

 heating, so as to allow the marble to pass completely 

 into it and leave about 1.25 inch of the tube free at 

 either end. On allowing the tube to cool, a perfect 

 contact between the iron and the marble was obtained. 

 In some experiments the tube was subsequently'" 



