172 LAWRENCE HARGRAVE. 
4. If a thread is tied to one end of the longer axis, and the 
segment held by the thread in the wind, if slightly rotated it 
will take up a position at a right angle to the direction the 
wind is blowing, and continue rotating. Plate vu, fig. 1. 
5. If the segment is mounted on its longitudinal axis it will 
remain stationary if the wind is blowing on either the 
concave or convex surfaces. Plate vui., fig. 2, Case 1. 
6. If the segment is placed in the positions shown in Cases 2, 
3, Plate viit., it will begin and continue rotating. 
7. If a finger is placed as in Case 4, the segment reciprocates. 
8. If the segment is plano-convex or semicircular in section, it 
will rotate under the same conditions. 
9. If two segments are substituted for the two opposite sails of 
a windmill, Plate viil., fig. 3, the two rotating segments will 
balance the two windmill sails when set at 45° pitch angle. 
Plate 1x. shows the detail of the air pump. 
It was now thought desirable to see what could be done with 
the available appliances towards making a steam motor. The 
conditions being that it should be lighter than the compressed air 
apparatus, have a uniform boiler pressure, and flap the wings of 
the standard size as fast as the compressed air engine did and for 
a longer time. 
The steam generator was at once recognized to be the main 
difficulty; and the Serpollet boiler was singled out as the germ to be 
developed. Steel pipe is not to be got in Sydney, so copper of 
ordinary trade sizes was procured. By the way, an English cor- 
respondent says that the ‘“Credenda” Seamless Steel Tube Co., 
Ld. is the only English firm which makes seemless tubes, but there 
is another in France whose productions up to one inch diameter 
are simply wonderful, for they can make a tube-y; inch diameter 
with a hole 3; inch diameter in the centre, ten feet long, all 
solid and seamless. . 
Quite a number of coiled, flattened coils and corrugated boilers 
were made and rejected. The one drawn, Plate x., is a two 
stranded coil and can easily be improved. 
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