Elastic Constants of Quartz Threads. 



103 



No. of 

 thread. 



Length 

 in cm. 



Diameter 

 in centim. 



Breaking 

 weight in 

 grammes. 



Fracture. 



3. 



30 



•0036 



34-34 



Close to bucket and half inch 

 from top, irregular. 



7. 



12 



•0020 



10-2 



Half inch from end. 



ame thread. 



CO 00 



Not 

 noted. 



•0016 

 •0016 



10-5 

 14-0 



Close to attachment (probably 

 due to vibration of bucket). 



In the middle. 



'12 ' 



d no. 



1 1 



• in. 



s i 



ra 1,12. 



15 

 12 



•0014 

 •0014 



10 

 9-2 



One inch from lower end, very 

 clean. 



Half inch from top, clean. 



10 



•0014 



9-2 



Close to upper attachment. 



■a 



n3. 



" Forgot 



•0014 



11-7 



Quarter inch from bottom, per- 

 fect point. 



*< 



14. 

 ,15. 



to be set 

 down." 



•0014 

 •0014 



8-2 

 8-2 



Quarter inch from top, not 

 clean. 



About the middle, clean. 



The diameter of these threads was measured with the help 

 of a stage-micrometer by Zeiss, which was afterwards found 

 to be correct by stepping it with a measuring-microscope 

 against the millimetre-divisions of a standard metre-scale, and 

 of a scale by the Darling, Brown, and Sharp Co. 



It is rather an interesting question as to what finally de- 

 termines the point where fracture shall take place. All the 

 threads were from very long pieces which had been shot, and 

 were very uniform. Some of the fractures indicate that at 

 the instant of fracture the material near the exact point of 

 fracture was in a very unstable condition. This is strengthened 

 by the observation that the pieces afterwards broke more 

 easily as a rule. The results are of value only as showing 

 what sort of loads can be carried by quartz threads of moderate 

 thickness, and as showing that Boys's estimate of a breaking- 

 strength of from fifty to seventy tons weight per square inch 

 of quartz section is confirmed. 



Measurement of Diameter of Threads. 



As the measurement of the thread-diameter was the funda- 

 mental operation in all the other experiments, it is as well to 



