Mr Whytock o?i the application of Oars to Steam-Boats, 39 
tliese holes slender rods were fixed at right angles from the 
cylinder. The skeleton of the screw being thus formed, a 
piece of soft twine was fixed to the first of these rods, close to 
the pole, and carried to the second, around which it was made 
to turn once, and then to the third, and in like manner along 
the whole of the rods. Then it was brought back in the same 
manner in an opposite direction. By repeating this process, a 
web was formed from the cylinder to the points of fhe rods ; 
and thus the form of the screw which I reckoned best adapted 
for the purpose was obtained. The rods being ten inches 
long, and the cylinder feet, and the screw consisting of 
turns, the mean angle at which the screw pressed upon 
the water, was one of 4?5 degrees. Pitch was then applied, 
to ^ve a solid body to the screw thus formed, and the web 
exactly resembled that of a ducky’s foot 
Having obtained the measurement, and the exact shape of a 
boat which lay at one of the lochs in the neighbourhood of 
Edinburgh, I had a frame made to support two screws, and of 
a shape and size to fit the boat ; because without getting a boat 
made for the purpose, I could not apply one screw alone. As 
soon the screws were let down into the water, and the boat was 
>pushed off by means of the boat-hook, the upright handles, with 
which the screws were intended to be put in motion, began to 
turn round in the opposite direction ; so that by this alone, the 
way in which they would operate became evident, although it 
was only the intended motion reversed. When force, however, 
was applied to turn round the handles, the breadth of the 
screw's, and their too deep immersion in the water, rendered it 
necessary to apply a degree of pressure which did not consist 
%vith their delicate structure, and the bevelled wheels, upon the 
axis of the cylinder, not having been sufficiently fixed, gave way, 
and parted from the axle, which occasioned the experiment to 
he put off, until they could be properly adjusted and made se- 
cure. Next day, however, I was denied the farther use of 
the boat, and obliged to relinquish all further experiments with 
the same apparatus, as it was made to fit this particular boat 
only. Perhaps this description of the invention and experiment, 
may induce some person in more favourable circumstances t© 
give a full trial to this scheme^ 
Edinburgh, Odoler 1, 1819- 
