PREVALENCE OF SPIRAL ARRANGEMENTS 



1 1 



Fifi. 3. — Study of a spiral sand-storm by the Author. Drawn'by C. Berjeau. 



at the same time. In water-spouts on land the upper cone consists of a mass of clouds, and the lower cone of sand, 

 dust, and other bodies found on land. Deluges of rain accompany their disruption." 



According to another authority (" Century Dictionary," edited by Dr. W. Dwight Whitney), " The water-spout 

 is a whirlwind over a body of water, which produces the appearance of a solid column of water, extending from the 

 surface to the clouds. In reality, however, the phenomenon that is seen is the cloud brought down to the earth's 

 surface by the rapid gyratory motion of a vertical whirl, and it consists simply of fine mist surrounding a central 

 axis of rarefaction. At first the cloud has the form of a tapering funnel ; then, descending to near the water's surface, 

 it draws up the water for a distance into its vortex, and imparts to it its whirling motion. The spout is then com- 

 plete, and appears as an immense column connecting sea and cloud, light in colour near the centre, but dark along 

 its sides. Like other whirlwinds, the water-spout has a progressive as well as a rotatory motion, its axis sometimes 

 being inclined forward in the direction of advance. ... It is common for a number of water-spouts to be seen simul- 

 taneously or successively " (Plate vi.. Figs. 1 and 2). 



Before leaving the subject of fluid spiral formations it may be interesting to direct attention to the spiral made 

 by the escape of ether in water placed in a red-hot silver basin (Fig. 4), and to the vortex ring made by smoke in its 

 first stage (Fig. 5), as delineated by Mr. F. Hovenden.^ 



The vortices formed by nebulaj are, in some respects, the most wonderful of all. So far as I can make out they 

 originate in three ways : — 



(a) Bv a nebular mass or nucleus assuming a rotatory or spiral motion in space and drawing towards it, in 

 well-marked spiral lines, smaller nebular masses ; (6) by a converse process, whereby the smaller nebular masses 

 assume spiral movements and coalesce to form a spherical or spiral nebular nucleus ; and (c) by a resolving or 

 disintegrating process, whereby the nucleus or central core throws off its substance in spiral streams, usually 

 two in number — these forming right or left-handed spirals. There is what is practically a spiral infolding and 

 evolving process at work ; a spiral overlapping in one direction, and a spiral unlapping in another and opposite 

 direction. 



There are good grounds for believing that spiral nebulous matter is not in every instance formative matter, 

 that is, spiral matter aggregating and building up stellar and other bodies. On the contrary, it may very well be 

 the spiral detritus of stars and other heavenly bodies breaking up and disintegrating. If this threefold view 

 1 " What is Heat and what is Electricity ? " by F. Hovenden, F.L.S., F.G.S., F R.M.S. London, 1900. 



