56 



NATURE 



{Nov. 2 1, 1878 



Grand. The appearance of this " distributor " is very 

 much like a miniature cart-wheel, about five inches in 

 diameter, inclosed in a circular glass-case, the spokes being 

 the twelve contact springs and the nave a small insulated 

 table which, when the standard automatically closes the 

 contact springs of the time-wire at the exact sixtieth 

 second every hour, is instantly carried down upon and 

 closes the twelve pair of contact- springs connecting the 

 twelve line-wires with their batteries. 



Many interesting methods have been adopted for testing 

 and other purposes of maintenance, but we have only 

 space to mention two. One is for the purpose of warning 

 in case of a break-down. This consists of an ordinary 

 electric clattering bell, with a small clock attached, and 

 also connected with the line-wire. So long as the time- 

 currents pass regularly through this instrument the alarm- 

 bell remains silent ; but five minutes after the failure of 

 any time signal to pass out upon its duty, the alarm-bell 

 begins to ring violently, continuing to do so for five 

 minutes, and then leaving a small drop indicator, showing 

 on which line the break-down has occurred. There is only 

 one alarm-bell, but each line requires its attendant little 

 timepiece (which, being "synchronised" by the passing 

 •current, never can be wrong) and drop indicator. The 

 other instrument is an alarum answering the following 

 important purpose : — A break-down being reported, a plug 

 is placed in a " bridge " corresponding to the number of 

 the line, which causes a very weak current (too weak to 

 affect any of the synchronisers) to pass out along the 

 line for the use of the linesman when searching for the 

 fault ; this found and repaired it is important that the 

 plug should be immediately removed : to call attention at 

 the office in Cornhill the linesman has only to break con- 

 tact at the nearest clock anywhere on the line to set 

 : the alarum going in the instrument room, when, the plug 

 being removed, the alarum is shunted off and the line 

 clear for work. 



We now come to the chief specialty of the system of 

 Messrs. Barraud and Lund, namely, the synchroniser. 

 This is an automatic finger-and-thumb action, brought to 

 bear hourly on the minute-hand, and bringing it, whether 

 fast or slow, "to time." Each synchroniser is complete 

 in itself, and is simply screwed behind the dial of the clock 

 to be synchronised. It is as follows : — 



Two levers carrying pins, and representing the human 

 finger and thumb, project through a slot in the dial (Fig. i), 

 and either^ close upon the end of the minute hand itself, 

 or upon a small block fastened to it underneath ; the two 

 levers have at their other end slots in which two pins 

 worlv, projecting from the keeper of an electro-magnet, 

 which, when magnetised at the given moment by the 

 closing of the contact springs on the standard clock, 

 draws the pins together, and sets the hand to time. A 

 reference to Figs. 2 and 3 will at once make the modus 

 operandi clear. E is an ordinary electro-magnet, G the 

 keeper, carrying a bar, H, and two projecting pins, K K ; 

 these act in slots L L in the levers M M, from the ends of 

 ■which project the pins o O (representing the human 

 finger and thumb) ; the passage of the current draws 

 down the keeper and bar, acts upon the levers M M, 

 closing them upon the minute hand of the clock and 

 setting it, whether fast or slow, to time. 



The following are some of the special advantages 

 claimed for this system : — i. That any number of clocks, 

 few or many, of any varying sizes, can be synchronised 

 to any agreed standard time-keeper. 2. That the 

 mechanism is, when not in its momentary use, entirely 

 detached from the works of the clock. 3. That it can 

 be applied to existing clocks by simply being screwed in 

 its place, and a narrow slit cut in the dial. 4. That any 

 failure in the transmission of the time-current leaves the 

 clock going in the ordinary way, to be ^'' set to time^' by 

 the next completed current. 5. That the clocks are kept 

 to time, whether having otherwise either a gaining or 



losing rate, even if such rate amounts to many minutes a 

 day. 



It will seen from the above description that the system 

 owes its success not to the discovery or application of 

 any new fact, such as that for which such eager search is 

 now being made to secure a perfect electric light, but 

 from the simplicity and efficiency of the synchronisers, 

 and their adaptability to every kind and size of clock. 

 By the simple expedient of winding the coils of all the 

 instruments with one size wire, any number, all of vary- 

 ing sizes and powers, can be connected up in circuit. In 

 the City circuit alone, which is wholly controlled by the 

 standard at 41, Cornhill, 108 clocks on eleven different 

 lines of an aggregate length of ten miles, and connecting 

 over eighty different establishments, are efficiently kept 

 to true time. Many more, we believe, are kept to time, 

 not only in other widely distant parts of London, but in 

 various parts of the country; for the latter purpose 

 Messrs. Barraud and Lund have a contract with the 

 Postal Telegraph Department for the delivery of time 

 currents at certain hours each day. There is now no 

 reason why all our public clocks at least should not be 

 included within the correcting power of this system, and 

 lead us astray no longer. 



THE TELEPHONE, ITS HISJO.iY AND ITS 

 RECENT IMPRO VEMENTS ^ 



in. 



The Carbon TelepJione 



IN the columns of this journal (Nature, vol. xvii, p. 

 512) the present writer remarked in the early part of 

 the year " that it was unlikely the telephone of the future 

 would employ the voice to generate the driving power, as 

 it does in the magneto-telephone, but only to modulate 

 the flow of a current obtained by coarser means. It is 

 in this direction that Mr. Edison is working, and his 

 practical triumphs in the past are the earnest of success 

 to those excellent telephonic investigations wherein he has 

 already won an enduring fame." Since those words Avere 

 written Mr. Edison has brought his telephonic experi- 

 ments to so successful an issue that his carbon transmitterj 

 and his new receiver leave little to be desired in electric! 

 telephony, except the automatic record of the received! 

 speech, and this, it is not impossible, may ere long be| 

 accomplished. 



The object Mr. Edison sought to attain was a variatioi 

 in the resistance of the circuit proportional to the motions 

 of the vibrating diaphragm of the transmitter. Graj 

 employed for this purpose a liquid resistance, but owing 

 to the fact that all suitable liquids are decomposed b) 

 the current, Edison abandoned them and tried solid! 

 conductors. He remarks in Prescott' s work on the tele-f 

 phone : — 



** In the spring of 1876, and during the ensumj 

 summer, I endeavoured to utilise the great resistance oj 

 thin films of plumbago and white Arkansas oil-stone, 01 

 ground glass, and it was here that I first succeeded ir 

 conveying over wires many articulated sentences." 



A spring attached to the vibrating diaphragm was 

 arranged so as to cut in and out of the circuit more 

 or less of the plumbago film. But the results were 

 not very favourable. In January, 1877, a new device 

 occurred to Edison, namely, the employment of 

 peculiar property which semi-conductors have, of varyij 

 ing their resistance under pressure.^ For this purpose' 



' Continued from p. 14. 



^ We have already considered in a previous article the historical facts con 

 nected with this discovery, and therefore it will be needless to refer to this 

 point here. A reference to the /our?tal Telegraphique of Berne for 1874. 

 wherein it was asserted M. CMrac had anticipated the use Mr. Edison has 

 made of the varying resistance of carbon dust under varying pressures, fully 

 confirms the statement we made in our lai^t article that the merit of this 

 application is not due to M. Clerac at all, who simply used permanently 

 compressed carbon dust as a rheostat. 



