232 /. Locke on the Electro- Chronograph. 



tricity acting on a chemical compound. It is evident that the 

 best imprint which a distant operator can make on this marking 

 machine to indicate an event, is to interrupt or disjoin the circuit, 

 and thus interrupt the line at that moment being generated. Most 

 of the electrical or magnetic clock machines mounted before mine, 

 caused only momentary shocks of electricity, leaving the elec- 

 trical circuit mostly open and without a current. Had they been 

 connected with either Morse's or Bain's recording instruments, as 

 mine is, the markings would have been dots and blanks, or Prof. 

 Wheatstone's would have marked alternately a line and a blank, 

 the blanks occurring in all cases while the circuit is broken and 

 held open by the clock. Suppose now, while the clock holds the 

 circuit open for a whole second at A, an observer distant a thou- 

 sand miles at B, wishes to make an observation at C still another 

 thousand miles off, what can he do ? He can break the circuit. 

 So he can, but the circuit is already broken by the clocks and 

 breaking it again in another place makes no change, a blank was 

 being generated, and it continues still to be a blank ; for when a 

 circuit is broken at one place it is broken in all places, and as re- 

 gards electrical action it is, for the time being, a nullity — has 

 no existence, and the distant operator can perform no action 

 through it. Such were the instruments of Messrs. Wheatstone, 

 Bain and others, set forth to a limited extent as the equivalent of 

 mine. 



5. The distant operations are confined, necessarily to positive 

 and negative effects, or to lines and blanks, and while the distant 

 clock chooses to hold the circuit open, the operator has no choice, 

 he cannot produce a position, viz., a dot or a line. He is there- 



fore confined to a negative, a blank, which he can command by 

 breaking a circuit otherwise every zvhere closed. Therefore, in 

 order to render the recording of observations, in the distantly 

 generated time-scale, possible, it is indispensable that the circuit 

 be kept dosed as nearly continuously as possible. It is a want of 

 attention to the fact that the operator cannot mark lines as well 

 as blanks at pleasure while the clock is operating, which has caus- 

 ed so many wrong and impracticable views to be taken of this 

 question. Such then is the condition of the electrical clock-in- 

 terruptor which I have invented. It causes the units of time 

 (seconds) to be marked by long lines interrupted by short breaks 



in order that observations may be recorded by longer breaks 



the « 



punctum of the observation being the commencement of the 

 break. 



6. As this commencement will sometimes happen within the 

 little break designed to mark seconds, I have devised the Metro- 

 tome key, which makes the observation break always of a uni- 

 form length, say half of a second, when its commencement can 

 always be deduced from its ending, and whenever that com- 



