WATEK-SPOUTS ON THE COAST OF N. S. WALES. 141 



cold space. The rising air under such an impulse would at once 

 be thrown into a well-defined vortex. In illustration of this we 

 refer to the water-spouts at Eden. There the cloud itself was seen 

 to be in circular motion, and therefore every vent in it with 

 uprushing air became a water-spout ; and the experience of Kaemtz 

 on the Rigi shews how rapidly comparative slight differences of 

 density and temperature may develop into a most violent vortex 

 or water-spout. 



Such are the simple and ordinary conditions which generate 

 water-spouts ; given the wide spread mass of shower cloud covering 

 many square miles of a warm ocean current, and water-spouts are 

 the natural and necessary result. Many vortices originating in 

 this way never run on to completion • a cone of mist descends from 

 the cloud as proof of the existence of a vortex motion, but this 

 must increase until the space from the sea to the clouds is spanned 

 by a vortex tube, which we call a water-spout. Many get half- 

 made and are seen as cones hanging down from the clouds; some 

 have cones from cloud and sea, and yet die away, but when these 

 upper and lower cones unite, instantly a new energy takes com- 

 mand and the cones contract, leaving a tube parallel from end to 

 end, and joining sea and cloud. The tube may be two or three, 

 or perhaps twenty feet in diameter, and it is so light that it sways 

 about like feathers and bends in curves before light winds. In 

 one remarkable case as we have seen herein, it stretched and 

 swayed about and formed a complete loop. So long as the tube 

 maintains its uniform size its life seems assured, but if it gets 

 uneven as in Plate 5, where it got smaller at the ends, and in 

 Plate 6 it got smaller at the middle; these conditions seem always 

 to indicate the approaching death of the vortex. 



The opinion that the tube when complete carries up large 

 quantities of water as a metal tube carries water, seems to be 

 held by many persons, but the facts here collected have convinced 

 me that it is erroneous. In the first place these water-spouts are 

 sometimes a mile long and vertical; if we suppose it to be full of 

 water and in a metal tube; the pressure on every square inch near 



