( 31 ) 



Investigations on the maximum strain of glass have been made 

 by Galitzin : ) and by Winkelmann and Schott 3 ). The former has 

 determined the inner pressure which cylindrical glass tubes can 

 resist, the latter two have determined the maximum strain of 

 glass rods. Galitzin's determinations, however, were made only at 

 relatively small pressures, those of Winkelmann and Schott only 

 at ordinary temperature. 



In our investigation we partly follow the method of Galitzin. 

 From the theory of elasticity we can derive in connection with 

 the dimensions of the apparatus the maximum tension in the glass 

 from the maximum pressure which the glass tube resists. The results 

 obtained in this way were compared with the direct data obtained 

 in a second series of measurements, where the maximum strain of 

 glass rods was determined. If we take into consideration the material 

 investigated, it is not astonishing that the results of the two series 

 show irregular differences. These differences however are of no 

 influence upon some general conclusions that may be drawn from 

 the measurements. 



§ 2. Determinations at ordinary temperature. 



Survey of the observations and arrangement of the measuring 

 apparatus. 



1. Determination of the maximum inner pressure. 



The experiments were made with ordinary Thiiringer glass. A 

 cylindrical reservoir of the glass to be investigated was fused 

 on to a thick walled glass capillary. The capillary was provided at 

 its end with a steel nut with a hexagonal part by means of which 

 it could be screwed on to a steel capillary which is connected to 

 a pressure pump with a metal manometer. For measurements to 

 200 atms. it was fixed on the glass by means of sealing wax, for 

 higher pressures it was soldered to the glass (comp. Comm. N°. 99 a 

 § 15, October 1907). If carefully made this connection proved able to 

 resist the highest pressures (1200 atms.) The tubes were previously 

 annealed carefully. 



According to their dimensions they can be divided into three kinds: 



a. thick- walled tubes with large inner bore. 



b. thick-walled capillaries. 



c. thin-walled tubes with large inner bore. 



It will appear that these three kinds of tubes give results different 

 for each group. 



x ) Bull, de l'Acad. Imp. des Sciences de St. Pétersbourg, Ve Serie, B. XVI N°. 1. 

 2 ) Wied. Ann. 61. 



