e. 
: 
Gould’s Report on Trans-Atlantic Longitude. 239 
These parts, as given in the Report, consist of the time requi- 
site,— 
1. For the signal to arrive at the other station. 
2. For the galvanometer needle to move through a percepti- 
€ are. 
_ 8. For the observer to notice the motion and tap his break- 
circuit key. 
4. For this observation-signal to be recorded upon the chrono- 
h 
ph. 
Of these the second and third constitute the “error of not- 
ing,” which is, therefore, partly instrumental and partly per- 
sonal ; the one due to the inertia of the galyanometer-magnet, 
the other being the “ transmission-time ” along the nerves from 
eye to brain, through brain, and thence to finger-tips; consist- 
ing, therefore, of three distinct intervals, viz.: 1, between phe- 
3, between volition and ng signal. m of these three 
tervals, according to the experiments made by Dr. Gould, 
co xceed, for good observers, 083; which woul 
_ With respect to Fis tout intervals which make up the quan- 
uty x, itis remarked that, if equal at the two stations, they 
ome wholly eliminated in the resultant longitude; if un- 
i ee the longitude must be increased by one half the excess 
of their sums for westward signals. In either case, the opera- 
tions for longitude give only their total sum at the two stations. 
The chronographs at both stations being similar, it might be 
in making the recor 
The method employed for determining the “ error of noting” 
1 ce 
was alike j d It was by carefull ob 
serving a series of sign a to thooe exchanged for Io : 
tude, and so that both the ori and 
o 
Same chro: te im respect to 
observation of the co uent deflection were recorded on the 
nograph. similarity 
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