258 
PROCEEDINGS OF THE VICTORIA INSTITUTE. 
suction-dredger of which the actual dredging gear is made very 
heavy and is used as a hammer to break up the rock. These 
have been used a good deal in America. In carrying away the 
dredged material care must be taken that it is deposited in such 
a position that if solid material it may not thereafter form an 
obstruction, or if soft may not be carried back by currents to 
the harbour from whence it has been removed. The spoil is 
sometimes used for assisting in reclaiming land. 
Reclamation . — Reclamation of land, besides being accom- 
plished by the processes previously mentioned, is also effected by 
warping, that is, by securing the sediment deposited by the 
tides, and this is done by running out groynes to check the 
receding tide and cause it to drop the solid matter held in sus- 
pension. When the ground has been raised as far as practicable 
by these means it is filled up to the height that may be desired 
by material deposited from the land. 
Jetties . — In cases where it is not possible, or would be too 
costly, to make quays and wharves having sufficient depth of 
water alongside, and where the sea will permit with safety of 
vessels lying alongside a jetty, in deep water, such a jetty is 
sometimes constructed. 
This may be either of timber or iron ; in many waters, 
however, timber does not last a very great length of time, being 
attacked by boring “worms,” as they are commonly called, the 
-teredo navahs being the most frequently found of these. In 
ng ish waters, though the Teredo is found, it is not nearly so 
arge 01 so destructive as the variety found in waters of warmer 
cJimates, and T have seen some piles which had been a consi- 
aerable number of years in the water, which when drawn were 
oun to e airly sound except for a few inches from the surface. 
Oreosoting timber protects it to a certain extent, but even this 
will not protect it where the worm is very voracious. 
r ™ n , JettieS are constructed of girder-work supported upon 
sunk ro il 61 ' SCrew -P lI f ° r , hoIJo ^ cylinders which, after being 
with con c ;L reqU1 6Pth bj excavati °S inside them, are filled 
have ’i h f a / en ° raI ske *° h of some of the work that may 
harbour InZ^l °'\ ^ Creation or improvement of a 
tt now Z 1 / 1 glance at the scheme of improvement 
mat is now being carried out at Port-of-Sm I r, t n 
starting from the corner of the Custom I • n f ’ 
angle a t a point in the line of the old St T T "5 
then be carried in the direction a ~ • * , ncen t Jetty, and 
west of the corner of Hip p • a P. 01nt a k° ut 150 feet south- 
corner of the Commissariat Wharf, usually known 
