WATER-SPOUTS ON THE COAST OF N. S. WALES. 143 



It thus appears that a water-spout of great energy may originate 

 under conditions in which little energy seems to exist; given a 

 massive cloud of great extent floating over warm water on a calm 

 day, and a water-spout may be formed at any moment. The 

 cloud is made up of parts of unequal density, and is necessarily 

 in constant motion, owing to the inequalities of its own parts and 

 the pressure of warm air from below ; if this motion makes a vent 

 or vertical hole in the cloud, the warm air flows up, gets some 

 rotary impulse and a water-spout is formed at once, its size and 

 energy depending upon the difference of temperature and elevation 

 between the air below and above the cloud. 



Every one who has watched great masses of cumulus clouds has 

 seen rounded masses rising above the general level; these are the 

 natural result of a vortex in the cloud bringing up the moist air 

 from its lower levels to its higher and colder regions, where it 

 deposits moisture and builds up the domes that cap the cloud. 



Appendix. — List of Thirty-eight Water-spouts seen on the 

 Coast of New South Wales. 



December 17th, 1888. — On the voyage of the s.s. Rotomahana 

 from Auckland to Sydney, she passed under masses of heavy rain 

 clouds, sixty miles from the Port Jackson Heads. From one of 

 the dark clouds a long tapering cloud descended, and a few 

 minutes later another tapering cloud formed and slowly descended 

 until it was the same length as the first, then both descended 

 until they reached the sea, which was immediately lashed into fury 

 and ascended in a cylinder form some twenty or thirty feet high. 

 Then suddenly the tapering form of the clouds changed to long 

 ribbon-like stripes, this lasted about ten minutes ; then a few vivid 

 flashes of lightning were followed by peals of thunder and the 

 water-spouts were dissipated in a heavy shower of rain. 



March 18th, 1891, South Head Signal Station, Sydney.— At 

 5 a.m. a heavy bank of cloud was seen coming from the south ; 

 from the cloud a large funnel shaped water-spout tapered to a 

 point at the sea, and when it had moved northwards and was due 



