( 35 ) 



TABLE III. Maximum strain of cooled glass threads. 



Stress 

 in grams 



Diameter 

 in m.m. 



I m 



in KG- mm- 



Stress 

 in grams 



Diameter 

 in m.m. 



Tm 



in KG/ mm" 



2920 

 3530 

 2120 



0.438 

 0.597 

 0.532 



19.4 



12. G 



9.5 



1910 

 17G0 

 2850 



0.325 

 0.322 

 0.445 



23.4 

 21.6 

 18.3 



With regard to the series of table III we may remark the following. 

 In order to prevent changes of form of the threads suspended in the 

 furnace and softened by the heat under the influence of gravitation, 

 which afterwards during the measurements might give rise to irre- 

 gular tensions, we have shaped the extremities (cf. § 2) not into 

 hooks as in the former series but to closed rings in such a way 

 that the whole becomes as symmetrical as possible with regard to a 

 plane through the longitudinal axis. A comparison of the tables II 

 and III shows that the two methods lead to the same results. 



Of the glass thread with the lowest T m (cf. table III) the section was 

 little ridged but smooth, to the next value of Tm (= 12.6) belonged 

 a relatively large smooth semicircular spot, while for the highest 

 T m (= 23.4) no spot was to be seen, but the whole section showed a 

 very sharply ridged structure. All these facts agree with what has 

 been found by Winkelmann and Schott ■). 



On the plate we show the structure of the sections of a couple 

 of threads at the place where the thread has broken. They both 

 clearly show the smooth parts and the structure radiating thence. The 

 smallest diameter of the sections is 0.530 and 0.555 mm. respectively. 



§ 4. Conclusions. 



Table I shows that as to the series a and c our results agree 

 tolerably well with those of Galitzin 1 ). 



Those of the series b, however, show that the result derived by 

 him for the maximum internal pressure, viz. 623 atms. is too low, 

 because the highest pressure observed by us is 1200 atms. For the 

 tubes of the series b T m appears to lie higher than would be expected 

 from the observations in the two other series. Probably this must 

 be explained as follows. From a comparison between the 3 series 



1 ) loc. cit. 



2 ) Table I p. 12 and 13, loc. cit. 



3* 



