CAPTAIN CARPENTER’S PROPELLER. 
61 
The arrangement consists in placing two wheels, of equal diameter, at the stern 
of the vessel, inclosed in a case. One is a little in advance of the other, so that 
the blades of one just clear the axis of the other. 
An iron steam vessel has been constructed by Mr. Napier for carrying this con 
trivance into effect, which, though obviously defective in form, (her after end 
terminating nearly in a square, and the propellers consequently consuming a 
large portion of their power in the dead water thus produced,) has attained a 
speed of 11 miles per hour. 
CAPTAIN CARPENTER’S PROPELLER. 
Fig. 55. Fig. 56. 
This arrangement has been adopted by the Admiralty in the pinnace belonging 
to Her Majesty’s steam vessel 4 Geyser,’ of which the inventor is Commander. 
There are in this case two propellers, which are placed in the quarters, as shown 
at figs. 55 and 56. They are moved by a rotatory engine called the disc engine. 
The propellers differ from all we have noticed, consisting merely of two flat 
trepeziums attached by arms to the axes. They are therefore not portions of a 
screw, though their action is helical. 
The experiments in this instance can lead to no results by which the efficacy of 
this propeller can be ascertained; the engine being of a kind which cannot be 
compared with the ordinary engines, and the pinnace is of such a size as will 
render it highly improbable she can ever come into fair competition with any 
existing vessel. We believe Captain Carpenter’s object is to reduce the direct 
resistance, on the assumption that the points of the blades are the leading points, 
and that the edge resistance will be decreased by the angles dividing the water 
like a wedge or the bow of a vessel. If such be his object (and we admit we 
may be wrong in assuming that it is so), he is evidently in error; for as the edges 
are radial, the direct resistance will be equal to that of the screw of the Archimedes.