OCT., igiO.j THE DECAY OF STONE ANTIQUITIES. IOI 
was required, and a grating was applied to the doorway, so 
that the door could be kept open, but no benefit has resulted. 
At present the cry is that the cause is wind action, and windows 
have been put into parts of St. Leonard’s Hospital. These 
two views cannot both be right. The inside also of St. 
Leonard’s Hospital, on the best expert advice, was washed 
over with limewash about three years ago, but it has all peeled 
off, and the entire inside surface, instead of being a mellow 
brown, is now one mass of whitish crumbling dust. 
Wind action is a well-recognised geological agent, and 
among its effects a polishing of the surface of the stone is 
mentioned in most text-books. It can polish concave surfaces 
as in the well-known Dreikanter (three-cornered stones) of 
the Egyptian and other deserts, and this has been claimed 
as characteristic of wind action. 
It so happens that, years before this idea of wind action 
was introduced here, I had paid considerable attention to 
the question of wind erosion, and had taken photographs 
of such examples as I met with in the deserts of Iceland. 
The best specimen (photograph shewn) was a surface of soft 
tuff or consolidated volcanic ash with larger fragments of 
harder stone embedded in it. The hard, sharp sand driven 
by the strong wind had eaten away the soft tuff, leaving the 
harder blocks standing up, and, the prevailing wind having 
come from one direction, the lee side of the stones had escaped 
and a tail remained behind each of them. The action was 
entirely a surface one, and the stone that remained was sound 
and uninjured ; no crumbling was noticed. 
I saw some very striking examples of wind action on the 
new ash of the 1906 eruption of Vesuvius. The old lavas 
near the observatory were covered with a layer a few feet 
thick. It had fallen gently and was in well-defined layers of 
slightly different appearance and from half an inch, or even 
less, to a few inches thick. When I was there a few days 
after the eruption, the deposit was rapidly consolidating. The 
wind carried the loose sand forcibly with it, and was planing 
off the projecting parts, exposing beautiful sections of the 
different layers. It was entirety a surface action. The 
parts which remained were entirety untouched and unaltered. 
I have seen the same thing on Haleakala, the great dormant 
volcano in the Hawaiian Islands. 
