1915] SUBMARINE BOoATs 129 
even amidships, because this form is convenient for boats designed for 
operating in shallow water. Some boats, such as those of the Germania 
type, have no frames. Other boats such as those of the Laurenti type 
appear to use the framework between the inner and outer hull as a means 
of stiffening the strength hull. 
STEERING AND NAVIGATION. 
Steering in a horizontal direction takes place as in ordinary vessels, 
but steering in the vertical plane has caused many difficulties to early 
inventors. As late as 1901 a German authority, Professor Busley, 
deprecated the value of submarine boats on that ground.* Mr. Holland 
introduced diving and emerging by inclining the boat at considerable 
angles, while most other inventors preferred to keep the boat as nearly 
as possible on an even keel and to effect great changes in depth by 
pumping water in o1 out of the boat, by means of horizontal propellers, 
or by so-called ‘‘hydroplanes’’. The last method is that which at pre- 
sent is mostly used in submersibles. Hydroplanes are similar to rudders— 
sometimes fitted amidships abreast of the centre of gravity of the boat, 
sometimes placed forward and turned the same way as the aft rudders. 
In all cases the object is to obtain an upwards or downwards force driving 
the boat laterally up or down. This method is generally considered 
safer than the ‘‘porpoising’’ used in the Holland boats. Once the 
desired depth is attained it is preserved by using the horizontal rudder 
in the same way as when steering a course on the surface, but with this 
difference, that even small deviations from the given course line (depth) 
are not here permissible. For guidance in steering a depth gauge and 
a clinometer are used. Steering in the vertical plane requires consider- 
able skill and experience. 
In order to navigate, the submarine boat must be provided with a 
reliable compass and, even when submerged, a view of the horizon must 
be obtainable at any time. An ordinary magnetic compass is not quite 
reliable even when placed in a conning-tower of bronze, but recently 
the advent of the gyroscopic compass has provided a means of accur- 
ately determining the direction. The faculty of vision when the boat 
is submerged, as it must be when making an attack, constitutes one of 
the most important and difficult problems connected with submarine 
boats. The water is practically opaque and it was therefore necessary 
in early boats, when going under water, to emerge from time to time 
so as to obtain a view from the conning-tower, but evidently this mode 
of navigation was anything but safe, since the presence of the boat was thus 
revealed totheenemy. Already in the “eighties’’ and “nineties’’ optical 
*Transactions of the Institution of Naval Architects, London, 1901, p. 188-189. 
gee 
