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248 \  - BLMONTHLY SUMMARY OF SCTENCE. | : 
IV Tie dipiculties incident tothe laying of long Hlectric Sea Cables. 
few people can imagine the great mechanical difficulties to be fovercome in 
laying a long eable. Owing to the dificulty of makings the joinines properly at 
sea, the rope cannot be carried out in more than two portions, and there are very ‘ 
few ships capable of conveying the required load in the necessary manner. Au * - 
electric cable is a difficalt thing to coil, indeed no one who inspects it in short . 
lengths would believe it capable of being coiled at all; the cable must, there- : 
fore, be laid in the hold, in as large a circle as possible, and the ‘space occupied ; 
must be perfectly clear from cross beams, or perpendicular supports for the deck. . 
The cable must be placed soas to load the vessel evenly, and must be so paid out i 
that she shall preserve an even keoi, otherwise water ballast must be admitted to —_ ‘ 
keep the vessel in trim. Moreever, with a jong eable, the vessel employed 8 
should be a steamer of sufficient dimensions not only to contain it, but coals ag ‘ 
well for the entire voyage, for if stowed in a sailing vessel and towed by a : 
steamer, the ship becomes in a heavy sea unmanageable, and in case of a hitch 
occurring, it is almost impossible to check her progress in time to prevent acci- 
dent. A cabletong enough to span the Atlantic will weigh at least 6.000 tons; 
and when coals must be carried, and in addition a clear space provided sufficient 
to enable this enormous length of cable te be coiled, it is evident that no existing 
vessel, except the Great Eastern, would be equal to the requirements of the case. 
The hands employed in liberating the cable eoiled in the hold have a dificalt 
task to perform, even when the sea is calm and everything goes on smoethly. 
When at full speed, the coils have to be carefully liberated, layer by layer, from - 
the lashings and packings of wood, so as to sel free only as much of the cable as | 
is required, 26 as to avoid the possibility of ils escaping from the guides on re- 
ceiving any check. The break is a part of the apparatus which requires the 
most delicate handling ; the strain which it puts on must be sufficient to prevent 
the cable fromm running out with too ereal a velocity in proportion to the speed - 
of the vessel, whilst it must be sensitive to every pitch and roll, in crder to pre- oS 
vent the cable trom heing snapped pya sudden strain, Many scliacting brakes, 2 
have been proposed, but in practice nothing has been found so effectual for the. 5 
regulation of the strain as Constant personal superintendence. The speed at 
which the paying-out vessel travels should be as uniform as possible thronghont — 
the whole voyage, and as provision must be made for contrary winds and rough 
weather, a large amount of surplus power is indispensable. in fair weather if is 
not difficult to altend to all these precautions, nothing but proper care and 
attention being necessary; but in stormy weather, when the vessel is tossing 
to such an extent that the men can searcely stand while unlashine and freeing 
the cable, when the pliching of the ship throws sudden and violent strains upon 
the break, and when the breaksman himself can scarcely keep his feet and can 
see nothing in the darkness, the difficulty of managing the apparatus properly 
is of no ordinary Bind.—Ze Quarteriy Journal of Science. 
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V.—Submarine Voleano in the Mediterranean. 
Letters from Malta mention an extraordinary convulsion of nature not fay 
from that city, between the island of Pantellaria and the town of Sclacca, on 
the coasi of Sicily, a submarine voleano having broken out about twenty-five 
: miles from the shore. Jt is said that a volcano existed there in the year 1701, 
i and onan old chart there is an old reef laid down precisely on the spot where : 
* the volcano now is. Ii was first indicated by smoke rising from the sea about oo 
the 12th of August last, which pradnally increased in volume for several days 
fill fire was seen, and eventuaily a small island was thrown up above the surface, 
about eighty or ninety yards long and twenty or thirty hich, composed of cin- 
ders. In its centre was the crater, which continually emitted steam and smoke 
CPE ES eile COR OBL as 
