i8o 



THE POPULAR SCIENCE MONTHLY 



tension of the whole contour. At length (Fig. 2, C 5) we find our- 

 selves in the face of that curious form of mobile equilibrium of fluids 

 of which we have noticed so many examples, and of which we have in 

 a manner just studied the genesis and the anatomy. These singular 

 wreaths have a still more singular constitution than we conceive ; they 

 are not full rings, nor even such simple hollow rings as we might make 

 by bringing together the ends of an India-rubber tube. We have to 



Fig. 4. A. Lamp-Chimney, closed by a membrane at its lower end, with a perforated disk in the 

 middle, and hall' filled with tobacco-smoke ; a push of the thumb on the membrane causes 

 rings of smoke to issue through the orifice of the disk in the middle. 



imagine a continuous necklace of watch-springs locked one to another 

 along a circle, by which all their ends are joined ; or, to speak geomet- 

 rically, the figure of revolution which would be produced by a plane 

 spiral turning round an asymptotic axis. Observation shows, together 

 with a delicacy of design in the shaft, and a transparency which nothing- 

 can excel, fine horizontal striae passing from one volute to another, and 

 marking with exceeding neatness the number and divergence of the 

 rollings. In water, effects of exquisite beauty may be produced di- 

 rectly without passing through the intermediate phases, by means of 

 taps on the membrane of the apparatus. The experiment may again 

 be simplified by forming with the membrane itself the bottom of the 

 vessel, and using for an orifice a hole pierced in a disk which has been 



