MECHANICS. 
fore, if the inclined plane is fifteen feet long, and its 
vertical height five feet, it will require nine feconds to 
move along the inclined plane, and but one to move the 
vertical height; and for this reafon the refiftance of the 
water to the air backwards being increafed in the above 
proportion, the lofs of force on this account will only be 
the difference between the aftual velocity of the motion 
of the fhip forward in a fecond, or the number of feet it 
will move in that time, and the meafure of the fpace 
which the air will move backward in the fame time; fo 
that, if the fhip moves forward ten feet in a fecond, the 
air, from the orinciples above dated, moving backwards 
but if feet in the fame time, the lofs of force will only 
be one-third, in thefe circumftances, of that acting on the 
inclined plane to impel the fhip. 
“ It might appear from the above, that, the fmaller the 
angle of the inclined plane, the greater muft be the effect 
of the air rifing beneath it, to force the fhip forwards; 
but this is limited by the quantity of air that can be 
forced out by the engine in a given time ; fince it is evi¬ 
dent, that, if the flope of the plane be fo fmall that the 
whole of the air cannot be fo confined by vertical fences 
running lengthways at its fides, that it will all pafs along 
it in the time of its afcent, but that part of it will efcape 
■under thefe fences, there muft be a lofs of power in pro¬ 
portion to the wafte of air: but, as thefe longitudinal fences 
may be brought down as low as the bottom of the veffel, 
and extend backwards as far as defired, it is evident that 
the angle of the inclined plane may be made very fmall 
without any lofs occurring from the above accident. 
“ It lias appeared from the calculations recited, that a 
fteam-engine of twenty-fix inches diameter in its main 
cylinder would produce air enough to difplace a weight 
of water equal to 2o8,448lbs. in a minute; and that the 
inclined plane can be managed fo that not more than a 
third of that force, or lefs, would be wafted in producing 
the defired effeft ; we may therefore afftime that the ef¬ 
ficient force of the engine will be 178,966^. in a minute, 
or agSzflbs. in a fecond. The Society for the Improve¬ 
ment of Naval Architecture publifhed experiments in 
1794, on the refiftance produced in bodies of different 
forms moving through water: from which it appears, that 
the one of thofe bodies, the moft like a fhip in fhape, the 
tranverfe vertical area of which in its broadeft part was 
5-78 fquare feet, required a weight of 27ilbs. to make it 
move eight feet in a fecond, or 5J miles in an hour. Now, 
as the force produced by the (team-engine before ftated is 
within a trifle of" eleven times that ufed to give the body 
mentioned the above velocity, we may calculate that it 
will give a vefl'el, of eleven times that area in its extreme 
breadth, very nearly the fame velocity; which area, fo 
determined, will be equal to eleven feet multiplied by 
fix, a fize fufficient fora fmall packet-boat for paffengers. 
And a (team-engine, of double the furf'ace in the pifton of 
that mentioned, or one a little more than thirty-fix inches 
in diameter, would impel a vefl'el of double the tranfverf'e 
lection of that ftated, or one feventeen feet broad and 
eight feet deep in its immerfed part, if flat-bottomed ; or, 
if of any other fhape, of fuch breadth and depth as to 
contain all together 132 fquare feet. The proportion of 
the fteam-engine to the fize of the vefl'el muft be greater 
than this if more velocity is required ; the exaft degree 
of which will of courfe be determined by experiment, if 
this plan fliould ever attraft notice fufficient to caufe it to 
be tried on a large fcale. 
“ I fliall next ftate the manner in which it feems to: 
me that this plan for impelling veffels may be bell put 
into execution. For this purpofe I would prefer a flat- 
bottorned vefl'el, whofe breadth fliould be three times its 
depth in its immerfed part, and its length at lealt four 
times its breadth. The head fliould be fhaped like that of 
a cutter, (harp below and broad above; and the bottom 
fliould be (loped upwards to the counter of the ftern, like 
that of a punt, only without leaving any angles, but fo 
as to form a fair water-way throughout; the angle of this 
Vol. XIV, No. 1013, 
789 
dope with the horizontal plane of the keel fhould be, I 
think, between 20 and 30 degrees; and I would be in¬ 
clined to make it rather lefs than this than more. At 
each fide of this (loped ftern, or run of the veffel, as it is 
technically called, (hould be firmly fixed a ftron<* vertical 
fence or partition, BB (fig. 129.) length ways, formed and 
arranged like the dead wood of a veffel, covered with 
plank, and connected with a ftern poit 1 the vefl'el thus 
having two ftern-poits and two rudders. Between thefe 
two partitions, a fpace of about fix inches or more in 
depth, and the whole breadth of the ftern D D, and a 
little more than half the draft of water down wards, fliould 
be inclofed parallel to the dope or run of the vefl'el, be¬ 
fore defcribed, by planks and bearing ribs, difpofed fo as 
to leave a free paflage from above downwards. At the 
lower part of this fpace the planks fhould be brought in 
fo as to make fair lines with the dope or run, and join- 
with it; and in this part it (hould be perforated with lon¬ 
gitudinal apertures, CCC, of an inch wide, fix inches 
long, and three inches apart, or thereabouts; and at its 
upper part it fliould be clofed by a Itrong plank, well fe- 
cured, where it fliould rife at lealt to the top of the coun¬ 
ter. From this part two large tubes fliould run alon°- 
under the deck, in the angles it forms with the fides, in 
order to take up lefs fpace; and for the fame purpofe the 
tubes might be made in the form of triangular prifms • 
by which fliape they would alfo have the advantage of 
fupplying the place of hanging knees in bracing the veftel, 
if made of materials ftrong enough for this purpofe, and 
properly bolted to the beams and the fides. Thefe tubes 
fliould lead to the blowing cylinder, or air condenfer, 
(formed on the principle of an air-pump,} and worked 
by the fteam-engine. The tubes and the inclofed fpace 
defcribed over the run outfide, which may be named the 
air-cafe, fliould of courfe be well caulked, fo as to be air¬ 
tight, and be fufficiently ftrong, and well faftened to bear 
the preffure of the air without hunting. The outfide of 
this air-cafe would form the inclined plane: by the aftion 
of the air along which in afcending, the veftel would be 
forced forwards. By having the paftage of the air thus 
entirely outfide the veffel, all neceftity of perforating the 
bottom of the veffel for the palfage of the air will be 
avoided, and all the rifk. attending on fuch perforations 
be removed. 
“ The broad fpace for the air-cafe is preferred to de- 
fcending tubes outiide, both to diftribute the air equally 
over the whole fpace of the inclined plane, and that every 
part of the paflage for the air may a< 5 t on its external 
part as an inclined plane, which would not be the cafe if 
defcending tubes were ufed ; for the air would then aft 
only in the fpaces between them, and would not be fo 
equally diftributed, and with fo little obftru&ion to the 
way of the veffel in moving through the water; the plan 
mentioned being fo contrived as to form no projections 
in the run, to avoid all perforations of the veffel below 
the water, and to diftribute the afcending air equally over 
the whole inclined plane. The reafon for dire&ing the 
air-cafe to defcend but little more than half the depth of 
the draft of water is, that the air, being compreffed more 
as it is forced lower down, in the proportion before ftated, 
lofes the degree of its force there mentioned in its re¬ 
action in afcending. 
“ A veffel might be conftrufted on the fame principles, 
with a Angle ftern-poft and rudder in the ufual pofition, 
(fee the figure,) by placing a vertical fence lengthways at 
each fide, as before defcribed in every refpeft. Thefe 
fences fhould be deeper near the counter from the bot¬ 
tom of the veffel than at their lower extremities, becaufe 
that the air, expanding as it rifes, will occupy a greater 
fpace in proportion as it comes nearer the furface, and 
will therefore require a deeper fence to confine it there. 
In this laft mode of conftruftion there will be two air- 
cafes, and two inclined planes, one at each fide of the 
ftern-poft; but care fliould be taken that they may com¬ 
municate with each other freely at top by a large pipe, or 
,9 P fowa 
