326 CHEMICAL MANURES. 



To obviate this, in the Bleichert system resistances are fitted on the 

 conductor at the passage of curves, so as to diminish the speed only 

 in the curved part of the course ; in the straight lines the speed is 

 a maximuED. Another pecuharity consists in the arrangement of 

 the points; so loQg as the apex of the points is not well closed a 

 commutator electrically isolates on the opening of the latter a 

 certain length of conductor up to the points itself. The car then 

 becomes stationary in front of the points if these are badly shifted, 

 which avoids accidents. The length of this insulated trunk is such 

 that the truck cannot reach the points in virtue of the acquired 

 speed. When it is not a case of heavy freights, the most practical 

 system is that in which the trucks accomplish a double journey on 

 the same line ; but in the case of important installations the railw-ay 

 is arranged in a circuit, so that the trucks can circulate in the same 

 direction and follow each other continuously. So as to stop or start 

 the trucks at any desired point, the naked conductor which trans- 

 mits the energy to the trucks is divided into sections, insulated the 

 one from the other, and as need be such and such sections are 

 brought into circuit or out of circuit by simple commutators working 

 automatically which can be placed at any necessary spot. 



The division of the line into separate sections has the advan- 

 tage of forming a block system, w^hich prevents any collision auto- 

 matically, and any shock between the trucks at the points or the 

 crossings. Each truck reaching a section interrupts automatically 

 by means of a commutator the current from the section it has 

 just quitted, so that the w^agon following, arriving on this section 

 which is thus out of circuit, stops of its owm accord. As soon as- 

 the first of the trucks just described arrives at the end of the 

 section w^hich w^e have seen it enter, it automatically turns a com- 

 mutator, which re-establishes the current on the section on w'hich 

 the following wagon is standing, which can in this way continue 

 its journey, repeating the preceding operations in the same cycle 

 for the truck follow^ing. In that w^ay no truck can reach crossings 

 and points until the wagon w^hich precedes is at a sufficient dis- 

 tance, and before it can pass them in its turn. 



This arrangement, indispensable to any suspended electric 

 railway on which a regular and safe service is required, produces 

 at certain points — for example, where the trucks are filled — the 

 following etfects. The truck reaches the spot where it is filled, 

 stops automatically, the current on the section on w^hich it is placed 

 having been cut by the truck ahead. The workman, the only one 

 generally required for operating these installations, opens the 

 valve w^hich shuts the hopper, thus allowing the matter to run into 

 the bin, and after having received its charge, brings the section 

 into circuit. . If, ownng to fortuitous circumstances, the loading of 

 the truck takes rather long, a larger number of wagons would arrive. 



