150 Captain Hall’s Account of" the Dundee Ferry. 
dious cabins. The machinery of the two steam-engines (each of 
W horse power), is concealed below; but the paddle-wheel, be- 
ing 14 feet in diameter, necessarily rises considerably above the 
deck, where it is covered by a wooden case. This wheel is 7 feet 
wide, and is immersed 18 inches in the water. It is a matter 
of perfect indifference which end of the boat goes foremost, both 
being alike in all respects. As the method of fixing the rudders,, 
one of which is fixed at each end, is, of course, different from that 
of a ship, it may be useful to describe it particularly. The rud- 
der is a plate of iron 4| feet long, and 3 feet deep. It is fastened 
to a vertical spindle, reaching from the middle of the stern to the 
water. In the first boat employed in the Tay, the rudder w 7 as 
attached by one end to the spindle, so that, when she was in mo- 
tion, its whole length trailed behind. But this rudder being 
found difficult to move, a device was adopted which answers the 
purpose perfectly. The spindle, instead of joining the rudder 
at the end, is fixed to it at one-third of the length ; so that, when 
the vessel is in motion, two-thirds are abaft, and one-third before 
the spindle, resembling a large weather-cock, or vane inverted. 
A horizontal wheel is fixed to the upper extremity of the spindle, 
and this is turned by a wheel and pinion by the steersman. Both 
the divisions composing each twin-boat are flat-bottomed, have 
perpendicular sides, and are sharp-bowed ; the angle at which 
the two bows meet at the extremities being 60°, ample room i& 
allowed for the escape of the back-water. The rudder is placed 
in the middle point between the two stems ; and, of course, lies 
directly in the centre of the current of back-water thrown out by 
the paddle-wheel. The steersman stands on a raised platform, 
above the taffrail, from whence he commands a clear view over 
the paddle-case. There are no masts ; and the only resistance 
which is offered to the wind is from the chimneys of the engines. 
Though the manner in which the two engines of a steam-boat 
are made to act in concert, be known to every person at all ac- 
quainted with the subject, it may perhaps interest some readers 
to describe, in a popular way, the beautiful device by which this 
object is accomplished. The paddle-wheel is moved by one con- 
tinuous shaft, to which both engines give their impulse, by means 
of two cranks, or bends in it, formed so as to be at right angles 
to each other. Thus when one of the cranks is either quite 
i 
