16 
HISTORY OF THE INVENTION. 
inserted a steel pin, which forms part of the hemispherical piece d, which consists 
of hardened steel, ec is a cast iron box securely bolted to the engine framing by 
flanges shown as broken off at ff. In the inside of this box a cast iron block g g 
is fitted, and there is a recess in its face into which is inserted a hardened steel 
plate h. It will be evident, therefore, that the effort of the screw to advance 
forward is all communicated from the hemisphere d to the plate A, and as the point 
of contact between the faces is a mere tangent, the friction must be inconsiderable. 
The box is filled with tallow, and as a further protection against friction and wear, 
a stream of cold water is allowed to run upon the working point of contact. 
This precaution is also observed in all the other bearings of the propeller shaft, and 
is effected by carrying a horizontal pipe along the side of the keelson, and having 
a series of small tubes affixed thereto, the open ends of which lead directly over 
the respective bearings, so that by opening a cock in the main pipe a jet of water 
plays upon the bearings, which afterwards runs away into the hold, and is pumped 
out by the bilge pump attached to the engines. This contrivance is found to be 
very effective, and in proof of its utility the steel plate h, and consequently the 
hemisphere d, do not exhibit much, if any, appearance of wearing. 
As one of the principal objects in the application of the screw as a propeller 
is to avail entirely of canvass where the wind is sufficiently favourable, a ready 
method of disconnecting the screw is of considerable importance. The method 
adopted in the Archimedes for effecting this will be understood by inspecting 
fig. 15. 
Fig. 15. 
The screw rests in bearings shown in the former figures, and at the fore end a 
coupling box c (the interior of which is of a hexagon figure) forms a part of the 
screw axis. The end of the propelling shaft d is made to accurately fit the recess 
in the coupling box, and an arrangement is made within the vessel so that the 
shaft can be drawn inwards through the stuffing box in the dead wood. When, 
therefore, the shaft is withdrawn from the coupling box, the screw is free to 
revolve in its bearings, and presents little greater obstacle to the vessel’s progress 
under sail than the friction of the bearings and the surface friction of the water 
passing over the threads of the screw. 
It is also necessary to describe in this place the provision for shipping and