Makch 23, 1883.] 



SCIENCE. 



187 



another five thousand dollars) , we would have 

 a sufficient basis for practical work. If the 

 result should be to increase bj- onl}- one-tenth 

 the beast-maintaining power of our wild lands, 

 the effort would be worth many millions per 

 annum to the nation. When we consider that 

 the introduction of the species of Poa which 

 receive the name of ' blue-grass ' has manifolded 

 the pasturage-value of the regions where it 

 flourishes, it is evident that the project is worth 

 consideration. N. S. Shalek. 



each of them is led a copper conductor to the 

 foot of the machine ; thence, along the masonry 

 foundation, it follows the ground (as shown in 

 Figs. 9 and 10), and arrives at a commutator 



HISTORY OF THE APPLICATION OF THE 

 ELECTRIC LIGHT TO LIGHTING THE 

 COASTS OF FRANCE.^ 



III. 



As the electric installation at the Planier 

 lighthouse is the newest and most complete, 

 some further details of its arrangement will be 

 of interest. The plan (Fig. 7) shows clearly 

 the position of the two generators, and of the 

 transmission-shafting which sets them in mo- 

 tion. 



Both generators are placed upon the same 

 masonry foundation, and their axes are in the 

 same line. In order, however, that one maj' 

 be ready to replace the other in case of acci- 

 dent, their shafts are keyed together ; and they 

 both turn, the one with an open, the other with 

 a closed circuit. Between the two machines 

 is a short column (shown in Figs. 9 and 10), 

 which supports the guides for changing the 

 belts from the loose to the fixed puUej's. 



Each machine is divided into two circuits, 

 shown bj' four terminals placed at the upper 

 part of the frame, two at each end. The two 



terminals placed beside each other at each end 

 of the machine are those which at a given 

 instant form poles of the same name. From 



1 Continued from No. 6. 



placed on the masonry column, which forms 

 one support of the shafting. One object of 

 the commutator is to take the current at will 

 from either machine ; another is to couple, 

 either in tension or quantity-, the two circuits 

 of each machine. The four possible combina- 

 tions of the commutator are shown in Fig. 11. 

 An examination of this figure shows that the 

 apparatus consists of fixed and movable con- 

 tacts arranged in a circle. The first are four- 

 teen in number. The four on the left are 

 in relation with the terminals 1, 2, 3, 4, from 

 which are led the conductors of the machine 

 on the left, or machine No. 1. The four on the 

 right are connected with the terminals corre- 

 sponding with the conductors of machine No. 2. 

 The three upper contact pieces are attached 

 to the terminals communicating with the con- 

 ductors of the lamp. 



It should be said, that the current reaches 

 the lamp by a large cable, then, after travers- 

 ing the arc, is divided between two smaller 

 cables, in one of which is placed the electro- 

 magnet of the lamp. Of the three upper con- 

 tacts, that of the left communicates with the 

 terminal E, to which is connected the cable of 

 the electro-magnet just mentioned ; the next 

 belongs to the terminal P C, of the second small 

 cable ; finally, the right contact, twice as large 

 as the others, is in communication with terminal 

 GC, of the large cable. This system of fixed 

 contacts is completed below by three pieces, 



