24 



COHESION FIGURES. 



be made by means of two wire rings, one having ahandle 

 the other three small legs. Both rings are wetted with 

 soap- water, and the one with the handle held horizon- 

 tally above the other which stands on its legs on the 

 table. A soap-bubble is now blown in the usual 

 manner by means of a clay tobacco-pipe between the 

 rings, and with a little care the bubble can be made to 

 attach itself without breaking to both rings, fig. 29, A. 

 The pipe is then cautiously withdrawn. 



FIG. 29 (an. prof. | real size). 



A contrivance, usually called a retort stand, is convenient for 

 fixing the upper ring in a definite position. A vertical rod, fig. 30, 

 is fixed in a rectangular board which forms the foot of the stand. 

 A ring capable of sliding along this rod carries a horizontal fork 

 of wood for holding apparatus of various kinds, which may be 

 firmly clamped between the prongs by means of the screw c. To 

 render the grip less hard, and thus to prevent the breaking of 

 glass vessels, the ends of the fork are lined inside with cork. The 

 fork is fixed to the sliding ring by the nut &, and may be placed 

 at any required height by the screw a. The figure shows a glass 

 tube clamped in a vertical position, but the fork may be turned by 

 loosening the nut 5, and anything held by it may thus be inclined 

 as required. 



If the upper ring is supported by the fork of the 

 retort stand, and made to slide slowly upwards, the 

 soap-bubble, which was originally spherical will become 





