that is, the force that prevents an ordinary vortex ring from collapsing on to itself.
Pending the complete hydrodynamic investigation of such a system as above sketched out, it must be regarded somewhat in the light of a speculation in which there is nothing actually
Fig. 81.
improbable. The conception suggests that if we had been called into existence surrounded by an atmosphere destitute of viscosity our natural method of locomotion would have been to glide horizontally sustained on the crest of a vortex hoop, a structure}}
Fig. 82.
which from its immutability would require to be specially created at birth, and would after death continue to pervade the world for all time like a disembodied spirit.
§ 126. Peripteral Motion in a Real Fluid.—In dealing with a real fluid the problem becomes modified; we are no longer under the same rigid conditions as to the connectivity of the region.
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