218 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



gas to enter the outer bubble the inner bubble will float like Moham- 

 med's coffin, suspended in space. I can now detach the outer bubble 

 from the ring by means of a second ring or by blowing a third bubble 

 in contact wdth the ring. Starting again, I blow a small gas bubble 

 in an air bubble held upon a ring. With a second ring I lay hold of 

 the outer bubble and draw it out into the form of a cylinder. If I 

 incline it alternately in the two directions, the inner bubble travels 

 backward and fonvard the entu'e length withm this cylinder. Again, 

 I remove the second ring and gradually blov\^ more gas into the inner 

 bubble. Thus I can enlarge it to the point of pulling upward suffi- 

 ciently strongly to support the ring and small objects suspended from 

 it. At no time, however, does the inner really touch the outer bubble, 

 though it supports the load carried by the latter. 



I begin again, and with one hand I place an outer bubble on a rmg. 

 I pass a ring into this outer bubble and then blow a bubble on it. I 

 then blow a third bubble containing gas in the interior of the other 

 tvv'o. I can then, at my pleasure, take away first one ring and then 

 the other, and thus render the three bubbles free, or transfer them to 

 another ring. It is possible, but not easy, to blow a fourth bubble 

 in the interior of the first three. However, it is not possible to follow 

 the same method as before, for we find ourselves limited by the 

 number of hands. 



If the two bubbles blown upon a ring are pressed against each other, 

 we have seen that they do not unite; but if the least electrostatic 

 attraction be established between the contiguous surfaces the imion 

 of the two bubbles is instantaneous and a single bubble is formed. 

 This can be accomplished by means of a stick of sealing wax, or of a 

 Morse key and wdres connecting the supporting rings to the terminals 

 of the electric arc. Two bubbles are much more sensitive than a gold- 

 leaf electroscope. 



I now take two bubbles, one within the other. If I bring a piece of 

 sealing wax near the outer bubble, the influence exercised can be 

 sufficiently strong to deform the outer bubble, but the inner bubble is 

 not afl'ected, for the electric force is nonexistent in the interior of a 

 conductor. I know of no other means of demonstrating the absence 

 of electric force in the interior of a conductor and at a distance from 

 the exterior surface less than one twenty-five thousandth of an inch. 

 The two preceding experiments may be combined mto a single one, 

 so as to show the contrast between the behavior of an outer bubble 

 and an inner bubble. The two outer ones join while the inner re- 

 mains unchanged. 



Now, that I have finished my task, I must express the hope that 

 the beauty of the phenomena which I have been able to show you 

 may persuade you to pardon me for any failures I have met, for one 

 can never be sure of succeeding every tune, and especially for the 

 small amount of purely theoretical interest" in this communication. 



