294 
Proceedings of the Royal Society of Edinburgh. [Sess. 
which attach the system to the frame /(fig. 12) ; and as the pivots P 2 P 2 be 
fore and aft with respect to the aeroplane, the brushes lie athwart the 
machine. 
Fitted to the base plate of the erector are two vertical pivots \ and , 
and on these are carried two rods terminating in weights w-^w ^ . The 
movements of these rods on their supporting pivots k-Jc^ are limited by 
checks , and by electric contact pieces and . k-^ and k^ are con- 
nected to the ring , d^ to , and d.^ to . The segments and are 
separated by insulated segments i i ; and and , together with the 
segments i, form a continuous ring in which press the brushes. 
For the particular scheme of operations to be now described one only 
of the brushes and is required (the function of the remaining 
brushes will be explained presently). One terminal of a battery is con- 
nected through a green lamp to the brush-holder of , and also through a 
red lamp to the brush-holder of ; the other terminal of the battery is 
connected to . 
Now consider the action of the device, as described, during ordinary 
flight of the aeroplane. The pivoted system is upright, so that the erector 
is horizontal. The brushes and 65 lie, as explained, athwart the aero- 
