Mr Fraser on a Method of Propelling Vessels. 117 
method of impelling steam-boats has been lately proposed in the 
Annales des Mines for 1820, p. 194, by M. Clapeyron, who does 
not seem to have been acquainted with the labours of preceding 
inventors. He supposes A and B, Fig. 4. Plate I. to be two 
apertures formed in the fore part of a boat, and communicating 
with a pump DA, in which is moved a piston P, driven by a 
steam-engine. If valves properly adjusted are placed at A, B, C, 
and D, the alternate motion of the piston will communicate to the 
water entering successively at B and A a force depending on its 
velocity, and on the ratio of the diameter of the body of the pump, 
and of the tube EF. This tube may terminate any where, pro- 
vided its axis is parallel to the direction of the current ; and the 
force which acts upon the boat will be always upon the side of 
the tube opposite to the orifice. By varying therefore the posi- 
tion of the orifice, and consequently the direction of the pres- 
sure, the boat may be easily guided without a helm. For this 
purpose, it will be sufficient to perforate the tube E F with la- 
teral apertures, which may be opened or shut at pleasure. 
M. Clapeyron supposes that the pipe E F should reach to the 
extremity of the boat, and that the water rushing in to fill up 
the vacuum might diminish the resistance of the current. He 
recommends also, that the orifice by which the water enters 
should be as high as possible, and that by which it issues as low 
as possible. 
In the year 1820, a joint patent was taken out by J. B. 
Fraser, Esq. and G. Lilley, Esq. for propelling vessels by 
forcing out a small jet of water by means of compressed air. 
This very ingenious contrivance, which, however, has not yet 
been put in execution, on a real steam -boat, is represented in 
Plate I. Fig. 5, 6, 7, 8, 9, where A B C D, Fig. 5, is a longitu- 
dinal section of the boat, and B C its keel. A cistern, or con- 
densing reservoir, E F, placed near the bow, has a main tube 
G descending from it, with a plug H, that may be opened and 
shut at pleasure. Two tubes, L L, Fig. 5, 6, branch off from 
G G, each of them having a plug O, by which it can be opened 
or shut at pleasure, and extend to a point rather nearer the bow 
than the centre of gravity of the vessel. The main tube G, after 
reaching a point Y, about one- third of the length of the vessel 
from the stern, divides into two tubes M M, Fig. 5, 6, which 
