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rOPULAR SCIENCE REVIEW. 
manded by Staff-Commander E. K. Calver. To the extensive 
and varied experience gained by him in surveying, is to be 
attributed in great measure the unexpected success which he 
attained in this new work, many of the expedients which his 
ingenuity suggested being of the utmost value. 
The sounding apparatus employed in deep water was the 
form adopted in H.M.S. Hydra , Captain Shortland, in sounding 
across the Indian Ocean, preparatory to the laying of a sub- 
marine cable. In order to obtain the depth correctly, it is 
necessary that the weight employed should be sufficiently heavy 
to make the sounding line run out with great rapidity. If this 
were not the case, and the line were payed out slowly, it would 
be liable to be deflected by Currents, and by the drift of the 
vessel at the surface, especially in a breeze, during the pro- 
gress of the operation, so that a greater depth would be indi- 
cated on the line than really existed. It is obvious, therefore, 
that in proportion as the depth is greater, and more line is 
employed, a heavier weight is required to counteract the in- 
creased friction of the water upon the line. In order to avoid 
the risk of breaking the line while hauling it in, and conse- 
quent loss of line and instruments, the following contrivance is 
employed, by which the weight becomes detached on striking 
the bottom. It consists of a cylindrical rod, about one inch 
in diameter, with a ring at the top to which the line is at- 
tached. A ring of iron slides loosely on the rod, and above 
this are cast-iron cylindrical weights, 1 cwt. each, perforated 
so that the rod passes freely through them. The ring and 
weights are kept in their place by a wire passing from the 
bottom ring to a small spring-catch above. As long as there 
is any strain on this apparatus, i. e. as long as it is descending 
vertically through the water, the weights are kept in their 
places, but when it strikes the bottom, the wire becomes slack, 
and is thrown off the spring, [releasing the weights, so that 
when the line is hauled in again, the cylindrical rod withdrawn 
from the weights is the only part of the apparatus that returns, 
bringing with it a small portion of the sea bottom, retained in 
its lower part by an arrangement of valves which it is unneces- 
sary to describe. The sounding line employed with this appa- 
ratus was specially made for this expedition, and though it was 
only 0*8 inch in circumference, its breaking strain was 12 cwt. 
It was marked at intervals of 50 fathoms, and kept for use 
wound on a large drum. 
The apparatus employed for temperature determinations was 
the result of much forethought and of many experiments made 
by the Physical Committee of the Royal Society. The expe- 
rience of former temperature-soundings tended to show that 
ordinary self-registering thermometers were liable, among other 
