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212 Application of the Galvanic Circuit 



wires by a star. I have known persons afflicted with deafness, 

 and, from that circumstance, compelled to resort to the use of 

 chronographs, to make more precise observations than those of 

 persons in other respects similarly situated ; but who, having 

 good sight and hearing, estimated fractions of a second by means 

 of the use of the eye and ear. I think we may assume, subject, 

 however, to correction by actual experiment, that the precision of 

 the combinations of sight and touch is to that of sight and hear- 

 ing nearly as seventeen to ten. 



This estimate supposes that no error is committed in the me- 

 chanical operation of imprinting and reading off. 



Now, this certainty is furnished for the first time in the history 

 of the science by die use of the automatic telegraph clock. The 

 objection to the use of chronographs in an observatory has arisen 

 from the uncertainty of their rates, and from the necessity of im- 



mediately transcribing and obliterating the record made on them 



for the purpose of identifying it, and preparing the dial for a 

 fresh record. Both of these objections are removed by the use 

 of the automatic clock register. 



The rate of this register has all the precision known to astrono- 

 mers. The length of a continuous fillet is limited only by the 

 size of the paper reels that maybe considered convenient for use. 

 An eight-day clock might be made to deliver a continuous grad- 

 uated register from one winding to another. 



A single label on any part of it, to identify one of the seconds, 

 fixes them all. 



I have before remarked that the error in the mechanical part of 

 imprinting a date on the automatic clock register, and in reading 

 off, need not exceed a hundredth part of a second. It may, in 

 fact, be reduced to a ten-thousandth part of a second by substi- 

 tuting for the paper fillet a metallic cylinder revolving like a 

 barrel organ, and graduating the seconds on a spiral line. Per- 

 haps Mr. Bains's method of registering on a paper, in a spiral 

 line, may supersede Mr. Morse's running fillet. 



The great advantage of the method of imprinting the dates of 

 bisections of a star, by the wires of a transit instrument, does 

 not depend merely on the increase of the precision of a single 

 result. 



The facility of acquiring the practical skill necessary for tap- 

 ping on a key, at the date of a visible bisection, is very great. 

 A few hours in this respect take the place of months, if not of 

 years, s|>ent in learning to associate together the sensations of 

 sight and hearing, so as to make a good transit observation. 



The third and paramount advantage of the method of imprint- 

 ing the dates of bisections of wires by a star, is in the sevenfold 

 accumulation of results in a single culmination, or in a given 

 period of time. 



