268 ELECTRIC LIGHTING. 



also provided with two lenticular arrangements for projecting 

 the image of the carbons on a screen, thus facilitating their 

 adjustment. 



Application to Nautical Signals at long range. 



Nocturnal signals exchanged between the various ships of a 

 squadron are often inefficient on account of the feebleness of 

 the light, and it would be desirable to make them clearer 

 and visible at a greater distance. To accomplish this, De 

 Mersanne arranged a particular system of regulator, which 

 could not only be controlled at a distance, but was also re- 

 gulated without requiring the presence of an attendant near 

 the instrument. 



This regulator has its carbon-holders mounted on two 

 vertical rods provided with a screw movement, and capable 

 of turning round on their own axes by an electro-magnetic 

 mechanism controlled by a commutator. The apparatus is 

 enclosed in a large lantern provided in its central part with 

 a cylindrical system of " lenses-in-steps," at the focus of which 

 the luminous arc is placed, and which is so arranged as to 

 direct the light according to the height which the beam has 

 to reach. Now it is in order to always keep the luminous 

 point in the right place that the above-mentioned electro- 

 mechanism is applied. This is composed of two straight and 

 two horse-shoe electro-magnets, arranged in two perpendicular 

 lines in a vertical plane. In the centre of these four electro- 

 magnets there is on a forked armature a lever provided with 

 a steel tooth, which passes between two parallel ratchets 

 inversely disposed to the lower end of the two rods of the 

 carbon-holders. When no current is passing in the electro- 

 magnets the tooth is exactly between the two ratchet-wheels; 

 but if, by means of the commutator, the current is passed 

 through one of the straight electro-magnets the upper one, 

 for example the lever already mentioned is raised, and the 

 tooth at the end enters between two teeth of the upper 

 ratchet-wheels, without, however, producing any effect ; and 



