SOME RECENT IMPROVEMENTS IN THE MECHANIC ARTS. 773 



The magazine is stored below the turtle-back and the charges are supplied to each 

 gun by separate pipes leading into the shield of each gun, and up through which, 

 prepared ammunition is forced as required. This construction admits of only one 

 man manipulating and firing the gun, including the great caliber centrally mount- 

 ed guns which are operated by steam-power. 



Great attention has been given of late, since Edison's widely published ex- 

 periments with the electric light. A late and novel means for adjusting the car- 

 bons employs three electro-magnets which control the same. One electro-magnet 

 in the main or arc-circuit, and a second in a derived or shunt-circuit of high 

 resistance about the lamp act upon the opposite ends of a common armature-lever 

 to establish the arc and operate the clutch mechanism respectively, while the 

 third is normally shunted out of the circuit by spring-contacts, which may be brok- 

 en when too great a current passes through the shunt-magnet around the lamp. 

 This third magnet is connected with devices for feeding or forcing the upper car- 

 bon forward positively when the clutch mechanism accidentally holds it. 



A novel pulley-band, for driving machinery consists of an elastic cord sur- 

 rounded with metallic rings or spirals. The spiral wire serves, it is said, to 

 protect the elastic cord from abrasion or wear, which would otherwise be very 

 great in cords of this description. 



A new safety device for telegraphic wires for preventing injury due to the 

 overcharging of the line, consists of two upright fiat springs electrically connected 

 in the circuit. Their upper ends rest normally in a notched end of a centrally 

 pivoted armature of an electro-magnet. A retractile spring operating against the 

 armature keeps its notched end over and in contact with the upright springs so 

 that the ordinary current used in working the line will not prevail over said 

 retractile spring. A dangerously strong current, however, causes the magnet to 

 overcome the resistance of the retractile spring and draw one end of the armature 

 down so as to free said springs from the other end and thereby breaks the cur- 

 rent. 



A new steam-engine, in its construction, proceeds upon the novel principle 

 of saving the latent heat in the steam operating a steam-engine, that is, to operate 

 the same to a high degree of expansion — say four times — and to form the space 

 or clearance in the ends of the cylinder, or its passages, of sufficient capacity to 

 contain the steam after compression by the reverse movement of the piston after 

 the expansion of such steam. No exhaustion of the steam is permitted after each 

 stroke, but the condensed steam or water is withdrawn by a pump and forced into 

 the boiler. The loss of steam, so condensed at each stroke, is supplied by live 

 steam from the generator. The operation of this engine is based upon the fact 

 that when steam is performing work in a steam-engine the heat contained therein 

 is converted into power, causing a corresponding decrease of pressure of such 

 steam. Consequently a less amount of power is regained to compress the steam 

 to its original pressure after working expansively in a steam-cylinder than it ex- 

 erted during the performance of such work. If a certain amount of steam is 

 admitted to a steam-engine cylinder, from which neither heat nor steam can es- 



