( 333 ) 
Art. XVI.-— Observations and Experiments on the Structure 
and Functions of the Sponge. By Robert Edmond Grant, 
M. D., F. R. S. E., F. L. S., M. W. S. 5 &c. Continued 
from p. 107. 
As the large fecal orifices on the surface of the sponge were 
the only entrances to the internal canals which had hitherto at- 
tracted the attention of zoologists, it was very natural for them 
to suppose that the nourishment of this animal is drawn into the 
body by these apertures, as by so many polypi ; and whether 
they supposed' this power of suction to depend on the fecal ori- 
gate, in 1761. During the war, when the price of copper rose from ll|d. to 22d. 
per lb., various substitutes were introduced. A gentleman of Devonport made 
an experiment on a ship named the Adventure. He caused one side of her 
bottom to be coated in the usual way, with pitch and tar, and the other with 
what is familiarly called Burning-house Stuff, (consisting of poisonous particles, 
taken from the chimneys of tin-manufactories), mixed with pitch and tar. On the 
return of this vessel into port, one side, to use the owner’s expression, 44 was like 
a hay-field,” whilst that on which the poison had been laid, was as clean as when 
she sailed. Mr T. Locke of Plymouth, also used a small barrel of the same sub- 
stance, mixed with the usual materials, on a large ship of 1000 tons ; and it was 
found to prevent the accumulation of weeds and barnacles. 
But though copper was found to preserve the bottom of a ship clean, the oxida- 
tion of this metal is so great, that, after a few years’ service, it has frequently been 
found to be utterly unfit for farther use. To prevent this waste from oxidation, 
and its attendant inconveniences, Sir Humphry Davy recommended the applica- 
tion of pieces of cast-iron, which, by a galvanic influence, should protect the whole 
body of the copper. The Pandora was one of the vessels fitted out under his di- 
rection about twelve months since at Portsmouth ; she is now undergoing repair 
at Plymouth, and particular attention has been paid to the effects of the experi- 
ment. It appears that the presence of the iron has completely prevented the oxi- 
dation of the copper ; but the bottom is so foul with weeds and vermes, that 
no one would have imagined she had been coppered. The Nightingale, Druid and 
Harlequin, which were also fitted on Sir Humphry Davy’s principle, have been 
found in a similar state, with the addition of barnacles ; and the iron used for pro- 
tectors, has been so acted upon, as to be found in a state of decomposition, reduced 
in weight about one-third, and presenting the appearance of plumbago. 
In short, although the experiment of Sir Humphry Davy has proved the power 
of iron to prevent the oxidation of copper, it has failed to cure the far greater evil, 
the accumulation of weeds and animals upon the bottom, to provide against which, 
copper was at first introduced. In the mean time, his Majesty’s Government, wo 
are informed, have decided upon discontinuing the practice of iron protectors, and 
orders, it is said, have been issued to that effect. — Edit. 
VOL. XIII. NO. 20. OCTOBER 1825. Z 
