The Atlantic C able. II 
and nothing can be more encouraging than the reports that 
the insulation i improves daily. 
A cable in the process of being laid ata uniform speed 
forms an inclined straight line from the surface of the sea 
to the bottom, so that "each part moves along one side of 
an isosceles triangle, the other equal side of the triangle 
being the line along the bottom which that part of the © 
cable will occupy when laid. The angle between these 
e jual sides shows the inclination of the cable in the water 
in the process of laying, so the transverse component of the 
cable’s weight in the water is equal to the transverse com- 
ponent of the resistance of the water to its motion. The 
tension where it enters the water is equal to the weight of the 
whole length of cable hanging vertically down to the bot- 
tom. Thus in laying last year’s cable at the depth of two 
miles, the ship going at the rate of six miles an hour, and 
the rate being seven miles an hour, the resistance to the 
egress of the cable, which should have been 28 cwt., was in 
reality only 14, owing to the frictional resistance of the 
water. Similar calculations have been made to show that 
at two miles depth the length of the cable forming the in- 
clined plane from the ship to the bottom was about seven- 
teen miles. While this fluid resistance thus greatly assists 
the laying by diminishing the strain, it offers scarcely any 
obstruction to the reverse process of hauling in should that 
become necessary, provided the speed of raising the cable 
do not exceed about one mile an hour. These consiilera- 
tions are of importance on account of the plan of the pre- 
sent expedition to raise and complete last year’s cable as 
well as lay the new one. 
There is no reason in science why this should not be 
done. Indeed, dynamics are quite as encouraging as the 
facts of last year’s attempt to raise it. The experience then 
gained, with stronger tackle and the improved machinery, 
presided over by eminent and practical scientific men, will, 
we trust, ensure the success of the attempt of 1866. 
Once laid there is reason to anticipate brilliant results. 
The gutta percha generally improves under water as it is 
now doing. The faults that have occurred to deep sea 
cables result from the joints, or from some imperfection in 
the manufacture, but so great excellence has been attained, 
that we may confidently anticipate the line once laid will 
not soon wear out. The Calais and Dover line, laid in 18 5, is 
now in working order. 
_ The following account of the differences between tie 
