INDUSTRIAL PROGRESS DURING THE YEAR 1875. cclxxiii 



adjusted or tuned to vibrate at a certain rate, differing from 

 that of any of the others, when under the influence of the 

 electro-magnet controlled by its corresponding key. These 

 several sets of electrical vibrations are transmitted through 

 the circuit without interfering with each other, in the same 

 way that any number of different sets of sound waves may 

 pass through the air without mingling or interfering. At 

 the receiving station each instrument is so adjusted as to 

 respond to its own special sets of waves, or vibrations, with- 

 out regard to others. By breaking and closing the circuit 

 upon the transmitting electrotome, so as to form telegraphic 

 signals, these are transmitted and taken up by the corre- 

 sponding receiving apparatus. Concerning the experimental 

 trials which are being made with this remarkable apparatus, 

 we learn that, while certain minor difficulties were shown to 

 exist, which it is anticipated may readily be overcome by 

 suitably modifying the transmitting apparatus, enough has 

 been demonstrated to show that the invention is destined to 

 become a very useful and important one. It may be re- 

 marked, incidentally, that one of the peculiarities of Mr. 

 Gray's system lies in the fact that while sixteen persons may 

 be using the wire, none of their messages need interfere with 

 the others, or become known to any of the others save the 

 sender and the designated receiver. On September 11th an 

 experiment test of the apparatus was made on a wire be- 

 tween New York and Boston (240 miles in length), over 

 which four separate messages were simultaneously transmit- 

 ted from Boston, and copied from four sounders by a like 

 number of receiving operators in New York. It must not 

 be inferred that the number of communications that may be 

 carried over the same wire simultaneously is limited to six- 

 teen, since in theory the system knows no limit as to num- 

 ber, and in practice the extent to which the multiple trans- 

 mission is carried will depend solely on the perfection of the 

 mechanism. We await the future development of this in- 

 vention with much interest. 



A brief abstract of the facts relative to the industrial em- 

 ployment of paper may not be out of place, in view of the 

 increasing importance of the subject. 



It has long been known to chemists that certain sub- 

 stances will act powerfully upon cellulose (or vegetable 



12* 



