A PRACTICAL METHOD OF SPONGE CULTURE. 561 
all rough, holes of considerable size were eroded in the sponge. Asbestos cord 
treated with rubber solution was least objectionable in this respect, owing to 
the softness of its surface and the firmness with which it could be gripped by 
the binding wires, the method of applying which is explained later. 
It was found that this difficulty of the corroding wires was obviated by the 
use of lead wire, to which the cuttings speedily form organic attachment and 
cling independently of artificial aid. The tensile strength of this metal is so 
low, however, that in spans it will not support itself, to say nothing of the 
weight of the sponges and the pressures exerted by waves and currents. To 
secure the virtues of lead, its freedom from corrosion, its chemically inert and 
innocuous qualities, and the facility with which the cuttings grow fast to it, 
while at the same time eliminating its defect of tensile weakness, the device was 
adopted of employing a strong fiber or wire core encased in a thin coating 
of lead. 
Several types of this construction have been employed with varying success. 
One of the earliest was ordinary tarred marline encased in lead about one thirty- 
second inch thick. This was light and when new quite strong enough for the 
purpose, but eventually the marline rotted and the lines broke, though some 
lasted for two years. Asbestos cord covered in the same way was also experi- 
mented with and found unsatisfactory. 
Several forms of lead-covered insulated wires have been used, but the ordinary 
commercial sorts have been unsatisfactory, being either too heavy and expen- 
sive, or, if sufficiently light and cheap, lacking in durability. Commercial under- 
writers’ wire with a copper core and specially encased in lead was superior to the 
higher priced insulations, and a still better wire was of the same type with the 
copper core replaced by galvanized iron. This had to be made to order, as there 
are no such insulated iron wires on the market. 
All of these wires and lines were used in the same general way, stakes being 
driven in the bottom in parallel rows at intervals of about 25 feet and the wires 
suspended between to form squares. At first the wires were attached merely by 
tying or winding them about the stakes, but it was found that this rigid attach- 
ment caused them to break under the repeated flexure to which they were sub- 
jected by swaying in the waves. Later galvanized rings were placed over the 
stakes, four wires radiating at right angles from each toward the adjacent stakes, 
the whole being supported at a proper height above the bottom by means of a 
short wire attached to the stake and ring, respectively. 
When lead-covered lines began to be employed they could not be attached 
directly to the rings on account of electrolysis, which would cause the iron to 
rust, and the rings were then wrapped with insulating tape to keep the two 
metals from coming in contact. Here another difficulty was encountered, the 
lead coating wearing through when loosely attached to the ring, or breaking near 
B. B. F. 1908—36 
