100 REPORT—1843. 
Qn the Marine Propeller invented about the year 1825 by Mr. Jacob Perkins. 
By Joun Isaac Hawkins, C.E. 
‘i his propeller is a species of screw, but distinguished from that called the Archi- 
medean Screw by revolving in a large circumference, and therefore requiring only 
a few revolutions per minute to effect a due speed of the vessel, and consequently a 
moderate number of strokes per minute of the steam-engine; distinguished also by 
about a fourth part only of the diameter descending into the water. 
It may be described as two sets of revolving oars or scullers, entering the water 
obliquely at the same time on opposite sides of the vessel, passing by each other 
at the middle, and receding from each other after passing the middle of the vessel, 
until they leave the water at the sides opposite to their respective entrances. The 
object of this opposite entrance and exit of the oars is to leave the rudder free from 
bias to either side, and thus to render the vessel easy to be steered. These con- 
trary motions are effected by fixing a set of four or six oars on the end of a solid axle, 
upon which another set of four or six oars, affixed to a hollow axle, revolves in a con- 
trary direction. Or the propeller may be said to be like two sets of windmill vanes, 
the solid axle of one revolving within the hollow axle of the other, the two sets of 
‘vanes moving in contrary directions; the axis of rotation lying parallel to and over 
the keel, at about half the radius above the water line, so that only the extreme half 
of the radius is submersed, the face of the vane having a variable obliquity, calculated 
to give the same degree of propulsive effect from every part, according to its distance 
from the centre of motion. The centre of rotation being out of the water offers no 
obstruction, like the middle part of the Archimedean screw propeller, which, being 
submersed, becomes a hindrance, the beneficial effect being only obtainable from the 
parts of the screw at a distance from the centre. 
Mr. Hawkins exhibited and explained a drawing of a propeller having two sets 
of six oars each, supposed to extend across the stern of a vessel thirty feet in width, 
the ends of the oars descending seven feet and a half into the water, constituting a 
propulsive effect proportionate to the velocity of the oars, combined with the obli- 
quity of their forces. The tips of the oars revolving in a circle of thirty feet dia- 
meter, the number of revolutions per minute will be but small compared with the 
Archimedean screw propeller; the necessary speed will therefore be easily obtained 
by ordinary gearing from a moderate number of strokes per minute of the engine. 
Soon after the date of the patent this propeller was placed to work over the stern 
of a canal boat, and driven by a very defective steam-engine. The circumference of 
the circle described by the tips of the oars was about 25 feet. The propulsive force 
was most strikingly effective, and was continued for a few miles, when a part of the 
steam-engine broke and terminated the experiment. It was witnessed, Mr. Hawkins 
said, to the best of his recollection, only by Mr. Perkins, by himself, by the engine- 
driver and by the stoker. 
He therefore feels it his duty to make an effort to rescue from oblivion this, in 
his opinion, the best of all marine propellers, which has laid dormant now for 
eighteen years. The patent expired four years ago. 
Mr. Booth described an apparatus for raising miners and minerals from the deep 
vertical shafts of mines. It consists of a revolving inclined plane, or endless screw- 
shaft. The threads of the screw are made to act on the peripheries of small wheels 
extending from the carriage in which the miners, &c. are placed. A rotatory motion 
is communicated to the shaft, and the carriage is raised or lowered according to the 
direction in which the screw is turned. 
Mr. J. Taylor described an immense steam-engine, which is now constructing in 
Cornwall, for the purpose of draining the lake of Haarlem. The cylinder of this 
*“ mammoth” engine is twelve feet in diameter, with a twelve-feet stroke. Round 
this immense cylinder are arranged eleven pumps, each of them of sixty-three inches 
diameter, with a nine-feet stroke. The valve at the bottom of the cylinder is on the 
butterfly construction, which is not generally conceived to be well adapted for large 
engines, 
