Star.
London, England, 1830-08-02 00:00:00

FIRST ACCOUNTS
'V Londe-es Expedition to Explore the River 11 iger.

It may be recollected that Lander, who accompanied Capt. Clap-
permit in his travels in Africa, and who continued with him till his
decease, was despatched by Government in the month of January
last, mime, if possible, the termination of the Niger. The fol-
lowing are extracts of two letters, recently received by Mrs. lan.
der, wife to the intrepid traveller, who is accompanied by hie
brother:—

-
" Cape Coast Cade, Feb. 43, 1880.
"We arrived here on Thursday loot, the 11/dt Lost. of an ex-
traordinary Sue passage, and were very kindly received by the Go.
vetnor, and, locked, by every other person. My former slaves, on
heating of my arrival, waited upon me, and appeared highly de-
lighted at seeing me again. 1 have engaged them to attend me
on our journey to the Interior of the country, and in the event of
our being visited with sickness, the slaves, who are engaged to carry
our luggage, will carry us in our hammocks; and 1 have every
reason to believe that they will do every thing in their power to
serve us, u they have been settled at Cape Coast several years, and
have wives and children, which they will leave here during their
absence, and will be a great inducement to them to do all in their
power to get back again, besides being a surety for their good con-
duct, as they will be afraid of being left behind. The Governor
of Cape Coast Castle has received a communication from the King
of Badagry, promising that he will direct every assistance to be
afforded us during our enterprise, which indeed is extremely
cheering."
" Accra March 13, 1830.
" We are now going on board the Alert, for the purpose of get.
Ling the baggage removed on board the man-of-war, which is ex-
pected to sail for liadagry this afternoon, and, should the weather
prove propitious, we shall reach there in about two days. My next
communication will be conveyed to England by the Clinker."
This is the only account from the travellers yet received. The
next, it is expected, will be very interesting.

SHEATHING OF SHIPS.
(From the Athenwunt.)

An important improvement in this useful branch of marine ar-
chitecture now awaits the sanction of successful experiments for
its adoption. To such of our readers as are not nautical, it may
be acceptable if we state that the adhesion of sea-weeds, and
certain species of marine animals to the bottom of a ship long at
i sea, offers a very great impediment to her progress. There is,
besides, a species of worm which eves its way into the timber,
unless protected by some external covering. Before the year 1775,
it was customary to cover the bottoms of ships with thin
planks, as it were to offer food for the injurious insects,
and prevent them from readily attacking the main tim-
ber. This, however, required frequent renewal, and
was no remedy against the attachment of weeds and shell-fish.
Sheet lead had been tried at an earlier period, and aban-
doned as unsuccessful. In 1758, a nisi was made on a small
frigate, of the effect of coppering the bottom, and though it was
found to answer completely, and is the method now generally in
use, the practice was not extended beyond the one solitary experi-
ment for nearly 20 years afterwards. It is now customary to cover
the bottoms of ships entirely with plates of copper, and it is found
that, while at sea, the copper remains petfecely bright, without
shells or weeds attaching themselves to it. It is commonly supposed
that the poisonous quality of the copper is the cause of its cleanness ;
and though it may have some effect, it is certainly not alone suffi-
cient to prevent the adhesion of animal and vegetable substances,
for when ships are laid up foe a long time in harbours, the copper
is much covered with weeds and shells. It appears to us, that the
brightness of the copper is chiefly owing to the oxidation of the
metal, and the removal of the oxide as fast as it is formed, by the
friction of the water as the ship sails. Thus the copper soon MIMI
out, which, on the score of economy, is a serious evil. Sir
liumphry Davy ascertained that the chemical properties of sub-
stances arc much affected by their state of electricity. If a
piece of sheet copper be immersed in dilute nitric acid, it
is acted upon and decomposes the acid, or, in other words, is dis-
solved ; but if the natural state of its electricity be changed from
positive to negative by the vdtaic battery, the acid has ni longer
any effect upon it. Now, with regard to sea-water, the copper, in
its ordinary state, is dissolved, but if it remain in contact with IMO
or zinc, a change of electricity similar to that we have described
takes place, and it is no longer acted upon by the water. Sir H.
Davy, therefore, thought that some such method might be prac-
demi with the sheathing of ships, and made seine experiments, but
unsuccessfully. The idea, however, has not been abandoned t
and we believe a scientific man of same eminence has hopes of
better WNW&

But if we fail in the application of the principle to the topper
sheathing of ships, it may be succesefully employed on other occa-
sions. Many important changes take place in consequence of the
electric action on metal.; sometimes the Wert is advantageous, but
frequently the reverse. Thus we me bens cocks in kaden cisterns
cotroded at the junction; iron railings inserted into atone with lead,
anyone's subject to dopy In the parte near the lead ; mud generally
soldered metals on roofs of houses are apt to decay and In eater
*way near the joints. It is raid also that breeze statues suppenod
by iron bars never acquire the beautiful peen not rot MOO/ adraired
in this country. The subject deserves loquby, porticsdoriP Mit
respects architecture, for the stability of maw( OUT thirst Iredklittlnt
I. found to be 'fleeted by the rapid oxidation of the ilOll cramp and
plop need in their cossatnectlon.