218 Mr. G. F. Rodwell on the Effects 



In the first and second experiments, in which the resistance 

 was least, we see that half a litre of water carried down 615 

 cubic centims. of air, a quantity (with one exception) more than 

 three times as great as that carried down in any of the other ex- 

 periments given above. The air escaped from C with perfect regu- 

 larity, and the results were very constant. In experiment 3 the 

 oritice of the tube B (fig. 1) was caused to touch the water- sur- 

 face in the vessel A, and we find a diminution of 70 cubic cen- 

 tims. in the amount of air carried down ; on further increasing 

 the resistance by causing B to dip one inch under the water- 

 surface (exp. 4), the quantity of air was at once diminished to 

 201 cubic centims. ; the air-disks were now formed higher in 

 the tube, and the air escaped from C irregularly, proving that 

 the disks were constantly broken, and that the air beneath them 

 escaped upwards; the highest of the disks formed at 15 inches 

 from the orifice of H ; the results were less constant than before. 

 In experiment 5 the air came over still more irregularly; in 

 other words, the disks were more frequently broken. In the 

 6th and 7th experiments we have obviously the same amount of 

 resistance as in exp. 5, but the orifice of B was free. In expe- 

 riment 8 we have precisely the same conditions as in exp. 5, 

 and nearly the same amount of air was carried down. In expe- 

 riment 5 the resistance was = 3 inches of water, for B dipped 

 2 inches under water, and there was 1 inch of water in D. 

 So also in experiment 8 the resistance was = 3 inches, because 

 there were 3 inches of water in D, and the orifice of B touched 

 the water-surface. In experiment 9 there were 4 inches of water 

 resistance, and in experiment 10, 5 inches. In experiments 11 

 and 12 the resistance was obviously the same as in experiment 10, 

 but the orifice of B was free. In experiment 13 we have pre- 

 cisely the same conditions as in the 10th experiment, and the 

 same amount of air was carried down. In experiments 14 and 

 15 there was still greater resistance; the highest of the disks 

 formed at 13 inches from the orifice of H. 



The conditions were now somewhat changed, the resistance to 

 the descent of air into A being greatly increased in consequence 

 of the air having to escape from an orifice one-eighth the size of 

 that used in the first fifteen experiments. In the 16th, 17th, 

 18th, and 19th experiments the resistance, as judged of from 

 the effects produced in the tube, was about equal to that in the 

 11th experiment. In experiment 20 the pressure was sufficient 

 to keep a column of water suspended in B at an unvarying height 

 of 11 inches from the orifice of H, and a persistent collision be- 

 tween the descending stream and the water-surface took place 

 at that height : the air escaped from C in a perfectly regular 

 manner, and the results were very concordant, not the least 



