NATURAL PHILOSOPHY. 113 



All the parts having been described separately, we will now explain their 

 connection, together with the manner of using the machine. The instru- 

 ments at both stations are first started, and made to revolve at the same 

 rate, the type-wheels lying in such positions that each time the arm of the 

 vertical shaft of one instrument passes over the slide of key A, the letter A 

 engraved on the type-wheel of the other instrument is opposite the paper 

 roller. To print a letter at the other end of the line, the operator presses 

 down the key on which the letter is engraved; the key raises the correspond- 

 ing metal slide which raises the revolving arm before one half of a second lias 

 elapsed, since the arm makes two revolutions per second. This makes the 

 current pass through the magnet of the instrument at the other station and 

 release its armature, which springs up. The detent acts instantly, makes 

 the chuck catch the printing shaft, and this last raises the printing roller 

 against the type-wheel, the letter is printed, and the armature coming down, 

 the printing shaft is unconnected, and every part returns to its original posi- 

 tion except the paper, which has proceeded the distance of one letter 

 forward. 



The closing of the current at one station acts only on the magnet of the 

 other station. This allows of the writing both ways at the same time. 

 Generally the despatches travelling in opposite directions are interwoven; and 

 also two different letters may appear to be, the one received and the other 

 sent at the same moment ; one, in fact, starts only after the other is arrived 

 and the way is clear; but, each time the same letter is transmitted by both 

 operators, the two machines act at the same mathematical instant. Two 

 batteries are erected, one at each station, and none at intermediate points of 

 the road, and they are connected with the instruments in a peculiar manner, 

 which will be best understood by making a diagram. One pole of each 

 battery is connected with the slides of the instrument, the other with the 

 ground. The wire of the line is connected at each end, through coil Xo. 1 

 of the instrument, with the upper portion of the shaft ; the lower portion is 

 connected, through coil No. 2, with the ground. When the keys of both 

 machines are at rest the current of both batteries is broken all the con- 

 necting wires and the line are free from electricity. "When a key is acted 

 upon in New York, the corresponding slide raises the arm; this disconnects 

 one coil in New York and makes the current of one battery pass through 

 one coil in New York and through both coils in Philadelphia. The power 

 of the springs acting against the armatures is so calculated as to overcome 

 the magnet diminished by the current of one battery through two coils, but 

 to be smaller than the magnet diminished only by one battery through one 

 coil. Consequently the armature in Philadelphia is released, and a letter is 

 printed there, and that in New York is held in place. The explanation for 

 telegraphing the other way is the same. When the sides of the same letter 

 are raised at the same time in both instruments, one coil of each is discon- 

 nected; but there is the power of two batteries in the other coil of each ; and, 

 as a power of two batteries through one coil is equivalent to that of one 

 through two coils, the result described occurs at both stations, and the letter 

 is printed at both places in the same identical instant. 



A second manner of using the instrument is to place the batteries on the 

 line as is usual, and to arrange the arms so that they clear the currents 

 when the slides come in contact with them. With this plan, it is not possible 

 to telegraph both ways at the same time. 



A third manner, which is favorite with the inventor, and which it is pro- 



10* 



