284 Origin of Steam-Boats, &c. ° . [Aprit, 
seribed harbour. An opinion may, perhaps, be entertained, that 
the water in this course, which is only five feet in breadth, will 
be apt to gorge in the space between the two wheels, by which 
the fore wheel would be loaded with tail water; but even if this 
effect should take place in the fore wheel to a certain degree, 
the after or sternmost wheel will work with greater advantage 
from the head thus supposed to be collected between the wheels. 
But when we consider that the vessel is afloat upon a great 
plane, and that the after wheel operates with the same velocity 
and effect as the fore wheel, and that even in the example 
before us they are placed 40 feet apart, it is not easy to con- 
ceive how the water is to gorge up in such a situation; it 
seems more probable that, the two wheels acting in perfect 
unison with each other, the water in the wheel course will 
preserve a smooth surface, and that the wheels will work 
with more advantage by being thus secluded and defended from 
the boisterous waves of the sea, than when exposed to them 
on the outside of the gunwales. Upon a tract of canal navi- 
gation, a steam-boat so constructed will not only pass along 
with great velocity, but without injury to the banks, which 
otherwise could not fail to be the case with the steam-hoat in 
common use. 
It is beheved to be a common prejudice with observers upon 
the deck of a steam-boat passing through the water, that there 
is a current Jeaving the steam-boat as quickly in a backward 
direction as the boat is making progress forward; but from the 
following experiment, and others which the author of this article 
has made, the apparent effect from the dapping or undulating 
appearance of the water, as seen in the work of the steam-boat, 
is apt to be mistaken for velocity in the water; whereas a little 
reflection, it is presumed, will convince every one, independently 
of the following trials, that this must be a deception. In the 
month of April, 1818, when returning from Inverary to Glasgow 
in the Argyle steam-boat, by Lochfine and the Kyles of Bute, a 
distance of upwards of 80 miles, which this boat performed in 
the course of 14 hours, a good opportunity was afforded of 
making various experiments with regard to the velocity of the 
boat, both im sheltered and also in somewhat exposed situa- 
tions, and in strong currents, both of the tide and of the 
river. About 50 pieces of birch timber turned into a spherical 
form, two inches* in diameter, were dropped from the vessel 
into the sea in all possible directions, when it was uniformly 
found that the balls dropped in the wake of the wheels of the 
steam-boat had hardly any sensible motion greater than that 
compared with those thrown at a greater or less distance from 
the boat ; or with those which were dropped into the water b 
the rudder case. This result one might have come to, @ priorz, 
by asking one’s self how the water in such a situation could 
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