176 Mr. H. B. Dixon and Mr. J. C. Cain on the 



In 1893 one of us published some preliminary experi- 

 ments by this method.* Tubes which stood a steady 

 hydraulic pressure of 25 atmospheres, were broken into 

 small fragments by the explosion-wave of carbonic oxide 

 and oxygen ; whereas, stronger tubes which stood a pressure 

 of 50 atmospheres were not broken by the explosion of 

 oxygen, either with carbonic oxide or with hydrogen ; on 

 the other hand, the stronger tubes which had withstood 50 

 atmospheres on the hydraulic press, were broken by the 

 explosion of cyanogen and oxygen in equal volumes, and 

 one of these tubes was broken at 78 atmospheres on the 

 press. It seemed desirable to repeat these experiments 

 and to find, if possible, narrow limits within which the 

 pressure of the explosion-wave must lie. 



Cyanogen was chosen as the combustible gas for most 

 of the experiments, because the carbonic oxide and nitrogen 

 yielded by its explosion with oxygen are simple in 

 composition and approximate in physical properties to a 

 perfect gas. Equal volumes of cyanogen and oxygen were 

 mixed in an iron gas-holder over mercury. The explosion 

 vessel consisted of a firing-piece with platinum wires, and 

 two metal tubes between which the glass tube to be tested 

 could be inserted by means of Faraday's cement. After 

 the apparatus had been filled with gas from the holder, the 

 taps were closed at each end, and a spark was passed. The 

 explosion-wave was generated in the first metal tube and 

 traversed the glass tube. If the latter held it was removed 

 and labelled, and another tube inserted in its place. The 

 glass tubes were about 20 cm. in length ; they were cut 

 from long tubes of fairly uniform bore and thickness of wall. 

 When a tube was broken it was our endeavour to gauge its 

 strength by testing hydraulically the strength of the pieces 

 cut on either side of it from the parent tube. 



* H. B. Dixon, Phil, Trans., Vol. 184, p. 150. 



