236 /. Locke on the Electro- Chronograph. 



key, I could, at any distance, print or write down on the Morse 

 fillet, the time in seconds or other units, represented by lines and 

 short breaks; and print into the lime-scale the exact moment of 

 an event, by breaking the circuit, and thus causing a blank or 

 break to be commenced in the line being generated. The plan 

 was immediately drawn, the work executed, and the actual ex- 

 periment made with perfect success. Almost every astronomical 

 observer has intuitively felt a desire to have some kind of a chro- 

 nograph with which to subdivide a second, and record fraction- 

 ally the punctum of his observation. The idea has undoubtedly 

 occurred again and again to the observer, that if he could have a 

 disk revolving with exact uniformity one inch or so per second, 

 and he could dot down appropriately in that inch his observation, 



without listening to. or looking at, a clock, it would greatly 



improve both his work and the means of performing it. Un- 



attained. 



perfect unif 



1 1. But in the electro- or electro-magnetic chronograph, although 

 perfect uniformity of motion is by no means attained, yet the 

 error thus arising is diminished to that which is inappreciable. 

 For as the velocity, although variable, is measured every second, 

 the only error necessarily created is that arising from the change 

 of velocity during one second of time, a quantity exceedingly 

 small. And even this small quantity may be quite removed by 

 finding its value from the law or rate of change exhibited by 

 several consecutive seconds, as indicated by the length of the 

 lines representmz them. The mean length of the lines preced- 

 ing and succeeding the observation second, will mostly give a 

 denominator so nearly of the true value, that, practically, the re- 

 sult may be considered quite perfect. 



12. As the invention was developed and perfected, a copy of 

 my journal of the work was currently transmitted to Prof. A. D. 

 Bache, LL.D., Superintendent of the U. S. Coast Survey, to con- 

 sult his opinion of its utility. 



Mr. Bache became so well satisfied of its value that on the 18th 

 of December, 1848, he made the request, by telegraphic despatch, 

 sent by Mr. Walker, that I would grant permission that he might 

 communicate it officially, in the form of a report, to Congress. 

 That permission was granted by me, December 20, 1848, and the 

 report was made. It seems, the sub-report of Assistant S. C. 

 Walker had already been written, as it was dated December 15. 



13. Letter of Prof Locke, published in the Cincinnati Daily 

 Gazette of Nov. 30, 1848. 



It will be understood by my last paper on the subject of a 

 Clock Register, that two kinds of marking upon the fillet of the 

 telegraph are contemplated. First, the register of time in hours 



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