2 72 BOTANICAL GAZETTE [OCTOBER 



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meniscus in a tube with a bubble pai?t which water flows should 

 be greater than in the same tube of unbroken water ; but at first 

 sight that looks unlikely. Some experiments seem, however, to * 



indicate that it occurs. Thus, in a tube 1.3™"' in diameter (as 

 nearly as I could measure), the height from the water outside to 



the meniscus within was 23"""^; with two bubbles in the 

 tube the height was 23.9"'"'; after they were removed it 

 was 23.1'""'. But in most instances I found the added . ; 



height, after introducing a bubble or two, to be about 

 0.1 """", which is too little to rely on as anything. Working 

 with a tube obstructed by a hair alone, I have seen a 

 bubble without any other provocation than an accidental 

 jar, slide above the hair and make a Jamin's chain, and 

 carry about 3™"" of water with it, so that the total water 

 held up was 27.2 """", instead of 24.2'""'. The energy to do 

 this must have been furnished by the change in shape of 

 the bubble. One more of these experiments will suffice. 

 A piece of glass tubing was blown in the shape illustrated, 

 and a bubble put in whose outline is shown by the curved 

 lines at the two extremities of the figure; a hair passing around 

 the bubble. Keeping the tube upright, it was subjected to an 

 added pressure of 70 ^'^ Hg. Within ten minutes the bubble was 

 reduced one-half, as represented by the inner bounding lines; 

 the immediate effect of compressing the bubble was to make 

 the meniscuses at its two ends of different shape, and this differ- 

 ence caused water to flow up around the bubble. 



While these experiments and others show the facility with 

 which water can pass bubbles in vessels of uneven contour, they 

 throw no light on the force which carries it around the bubbles 

 in the tracheae; which is the question that needs answering. The 

 ease of the movement, and its rapidity, and above all the pressure 

 relations involved in the tracheae, are still quite in the dark. 

 Since the water moves farthest and fastest here, it is greatly to 

 be hoped that physicists will soon take a position with which we 

 can get in touch. 



Another problem hardly less in the dark than the physics of 



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