48 Proceedings of the Royal Irish Academy. 
The crew consisted of the captain, chief engineer, and eight men, 
all told. 
Sounding Machine. 
Sir "William Thompson was, I believe, the first to use fine steel 
wire on a reel with register on axle for measuring depths. His method 
has been tested on a large scale by the American Government, and the 
celebrated soundings of the United States American frigate " Tuscarora" 
were made with a machine on this principle. 
Captain Sigsbee improved upon Sir William Thompson's apparatus 
in various ways, chiefly by the addition of an accumulator ; and so far 
as was possible with the funds at my disposal I copied Captain Sigsbee' s 
machine in constructing an apparatus for our expedition. 
Oar machine consisted of a cast-iron reel, 17 inches in diameter, 
with a groove, 2 inches wide, on which was wound the steel wire. A 
second groove, Y-shaped, was for a friction-line which controlled the 
speed of the reel. A screw-thread on the axle engaged the cog-wheel 
of a register which recorded revolutions.^ The wire, on leaving the 
reel, passed over a wheel supported by spiral springs capable of bearing 
a strain of 180 lbs. When the sounding-lead was hanging on the wire 
ready for or during a sounding, these springs were at stretch ; to the 
frame of this wheel the friction line was secured, which, after passing 
through a pulley, passed over the friction groove of the reel, the other 
end being made fast below. The effect of this arrangement was, that 
so long as the weight of the sounding-lead was in suspension the wheel 
was borne down, the friction line kept slack, and the reel free to re- 
volve ; whereas, the moment the lead reached the bottom, the springs 
were released, the friction line pulled taut, and the reel so gripped by 
it that it must cease to revolve. The register could then be read, and 
the depth ascertained. 
In the greater depths we utilized the friction groove for a rope belt 
to the donkey-engine, and so hauled back by steam. The lead used 
was an ordinary one of 15 lbs.; this weight at least was necessary in 
order to bring the springs into action. We did not find it necessary 
to use a heavier one, nor to resort to a Fitzgerald sounding-rod with 
detaching weight, which we had on board. 
On all previous occasions on which soundings have been made with 
wire, the kind used has been piano wire, 22 Birmingham wire gauge. 
1 Amongst his many other services, we must thank "W. H. "W. Perrott, Lieut. 
E.A., for making this register and its fittings. 
