560 BULLETIN OF THE BUREAU OF FISHERIES. 
various patented compounds of rubber, etc., which have been found to possess 
superior properties for electrical purposes, soon developed their worthlessness 
for sponge culture, the insulation being affected by salt water and stripping 
from the wires. Underwriters’ insulation, so called, a cheap covering of cotton 
and white lead, proved to be more durable and lasted for upward of two years, 
but it, too, eventually stripped or crumbled from the wire. Ordinary telegraph 
wire electrolytically galvanized rusts very quickly and breaks into pieces. 
Iron wire galvanized by the “hot process” will last for a number of years if 
kept fully immersed in sea water, but when it is periodically partly exposed 
at low water it rusts more quickly, and moreover the zine coating kills that 
part of the cuttings brought into contact with it. Iron wire coated with lead is 
also quickly destroyed, and copper wire coated in the same way kills the sponges. 
Plain or ‘‘black” iron rusts quickly and breaks, and the iron salts are injurious 
to the fiber of the sponges. Aluminum wire is innocuous as to its salts in sea 
water, but is rather expensive when of sufficient diameter, and is subject to 
rapid corrosion in spots, causing it to break into pieces. 
Asbestos cord was found to be practically indestructible chemically, but 
when wet the fibers become loose and frayed and so slippery that the tensile 
strength is seriously reduced. This difficulty was overcome by treating the cord 
with rubber solutions, white lead, a mixture of paraffin and asphaltum and 
other waterproofing and cementing substances. This treatment very greatly 
increases the strength of the cord, especially in the water, but the rubber is 
somewhat expensive and the asphaltum, despite its mixture with paraffin, has 
an abrasive effect on the cuttings and wears large holes where the cord passes 
through the growing sponge. 
Jute, sisal, manila, cotton, and hemp lines were employed, but as expected, 
they were all quickly destroyed in salt water. Coir (cocoanut fiber) rope was 
not experimented with, as there was some difficulty in obtaining it, and more- 
over, experiments with the fiber showed that it, too, is more or less quickly 
rotted in the water. 
Stakes and other wooden structures placed on the bottom are quickly 
riddled by the teredo and other boring organisms. If planted green with the 
bark on they will last longer, but the bark of the most durable, the mangrove, 
has a bad effect on the sponges, while that of other trees tends to scale off after 
a while, the sponges becoming detached with it. If there were no better method 
available, black mangrove and white wood stakes stripped of bark would prob- 
ably hold together for four years, but to prevent rotation and capsizing they 
must be nailed together in frames. 
To none of these materials, excepting the barked stakes, did the cuttings 
make organic attachment. When the artificial attachments loosened, the 
cuttings were free to rotate and drift on the wire, and when the latter was at 
