Makch 16, 1883.] 



SCIENCE. 



163 



and', without traversing the commutator, goes 

 bj- the cable to the regulator (or lamp) ; thence 

 it returns bj- the second wire of the same cable 

 to N, follows the vertical conductor to P, and 

 returns to the machine by the rod B. If it is 

 desired to use the machine corresponding to 



the rod B'. the central handle is turned, thus 

 bringing the plate D in contact with P' instead 

 of P, retaining alwaj's the contact at N. In 

 this case the current arrives, as before, at A, 

 goes to the regulator, returns again, but passes 

 this time from N to P', and thence to the ma- 

 chine bj' B'. 



In foul weather, or whenever it is necessarj' 

 to increase the luminous intensity, both ma- 

 chines are coupled in quantity. The commu- 

 tator is then turned until the plates E and E' 

 are in contact, — the one with P' and N', the 

 other with P and N ; the return current flowing 

 simultaneously by B and B'. 



The tower of each light is surmounted by a 

 square structure, at one of the angles of 

 which is the optical apparatus. This is clearlj^ 

 shown in Fig. 3. A kind of glass drum closes 

 the open angle of this structure, which is in 

 two stories, in each of which is a distinct opti- 

 cal apparatus. The intention of this arrange- 

 ment is to allow one optical apparatus to be 



instantlj' replaced by the other, in order to 

 avoid total extinction in case of accident. In 

 each story, there are two regulators, which can 

 be substituted * for each other bj^ means of the 

 crossed rails shown in Fig. 4. The cable with 

 three conductors leading from the commutator, 

 previouslj- described, arrives at the lower story. 

 One of the conductors (A) is connected to the 

 metal platform carrjang the rails, also metallic ; 

 the conductor B connects with the sliding rod 

 of the long bolt M T. When this bolt is low- 

 ered, it connects the conductor B with a wire 

 going from the bottom staple of the bolt to a 

 spring contact under the lamp. The latter re- 



ceives the current, partly bj' the rails, partly b}' 

 the contact underneath. The wire B communi- 

 cates with a smaller bolt sliding at the same time 

 with MT, and whose lower staple is conuected 

 to the wire coming from the staple of the larger 



