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principle ot gyration might be advantageously employed to 
neutralize the action which the wind and waves exert upon 
floating light ships. 
After briefly describing the principal features of the 
catoptric and dioptric systems, Mr. Roberts stated that the 
latter was inapplicable to floating beacons, owing to their 
great oscillation, and that they were therefore still furnished 
with 12in. reflectors, whose power was comparatively small. 
He felt convinced, however, that the more fully the system 
ol Mons. Fresnel became understood, the more certainly 
would it be preferred to the catoptric system, over which it 
possessed, among other advantages, that of producing about 
tour times the amount of light as the effect of the combustion 
of the same quantity of oil. 
It was, however, essential to the adoption of this system, 
that the light apparatus be kept upright and free from 
oscillation, to attain which desideratum Mr. Roberts proposed 
entirely to change the form of the vessel, making that portion 
of it which was immersed hemispherical, and that which was 
above water the frustrum of an inverted cone, as he thought 
that this form would present less resistance to the wind and 
waves, where these were expected to act from every point. 
In certain situations, however, a double pointed vessel might 
be advantageously used. 
In the centre of this float Mr. Roberts proposed to build a 
tower (whose lower end should project through the bottom of the 
float to serve as a keel) carrying a lantern asin shore lighthouses, 
and containing the necessary accommodation for the light 
keepers, &c., and within this lantern he proposed to place a 
dioptric apparatus of the second power, whose light being placed 
forty-five feet above the water line, might be seen at a distance 
of nine miles. Immediately below the light apparatus he would 
place a fly wheel suitably mounted on gimbals, and driven 
through the medium of' certain wheels and shafts by a small 
engine, which with its boilers, would be placed on the third deck 
