688 Prof. J. Joly on the Closure of Small 



test: the grain is alike. It is probable the difference is 

 quite unimportant. In all particulars the arrangements 

 were same as in (I.). 



The test extended from March 6th, 1913, till June 24th, 

 1913, ?'. e. for 110 days — during which time a pressure 

 of 30 tons on the plunger was steadily maintained. On 

 relief of pressure it was found that there whs no debris in 

 the cavity in the basalt, but reflected light revealed a faint 

 but unmistakable distortion of the flat covering surface. 

 The appearance is that of a thin protuberant ring ; but close 

 examination shows a raised circular area of the diametral 

 size of the cavity. 



The cavity in the granite sphere contains debris, but the 

 breakdown is less than in experiment (I.). The flat surface 

 covering the cavity shows signs of cracking- 

 Photos of these effects are given in figs. 3 and 4 (PL XVI.). 

 We must conclude from this result that 30 tons pressure, 

 even when exerted over the brief period of 110 days, has 

 broken down the granite and produced a distortion of the 

 basalt which remains as a permanent set. In short, there 

 has been something like flown ge. Prolonged over years or 

 centuries— even at these low temperatures — such distortion 

 would very surely ultimately close the cavity. 



(III.) In this experiment the arrangement w<as somewhat 

 different from that of (I.) and (II.). 



Two spheres were dealt with, A and B. 



A consisted of a hemisphere of basalt and one of granite 

 separated by a thin ground-steel washer, closely 0*5 mm. in 

 thickness. 



B was similarly constituted. 



Canada balsam cemented the hemispheres together in both 

 cases. It will be understood there is no cavity in any of the 

 hemispheres. The opening in the washer is of the same 

 diameter (b' - 2 mm.) as the cavity existing in (I.) and (II.), 

 and the observation is confined to effects of distortion of the 

 flat surfaces covering; this opening at either side. 



A pressure of 20 tons was applied from October 13th, 191 ?>, 

 till March 21st, 1914, i. e. for 150 days. 



It was then found that both the hemispheres of A showed 

 visible but not very definite effects. In the case of the 

 granite there is some fine hut distinct cracking around the 

 margin of the central circular area of relief of pressure. The 

 basalt showed one fine crack touching this central area 

 tungentiull j. 



