150 On the Application of Galvanic Electricity 



employed in an observatory, it becomes a matter of the first 

 importance to determine their personal equations, in order 

 that all observations may be reduced to a standard. 



In the chronographic method no listening to the clock is 

 required — the clock may be in another apartment, if neces- 

 sary — no recording by the observer during the observation is 

 needed, so that the intervals between the wires may be re- 

 duced from fifteen to three seconds ; the observer's attention 

 can be entirely confined to the observation itself, and is not 

 distracted between observing, listening, and writing, and the 

 precision attainable is at least ten times as great as by the 

 old method. Personal equation is greatly reduced, if not 

 eliminated. 



Any one acquainted Avith the principles of physiology will 

 at once perceive the great superiority of the chronographic 

 registration over the eye-and-ear method. In the latter we 

 have two totally distinct external impressions, the view of the 

 star crossing the field of the instrument, and the sound of 

 the clock-beats which require to be mentally counted at the 

 same time ; while in the method now adopted we have only 

 the one external impression — the view of the star. The 

 mental operation involved, in coinciding thus with the touch 

 of the finger on the key, being so rapid as to be almost inap- 

 preciable. 



Again, the record on the register-paper is permanent, and 

 in case of an error in transcribing, can be afterwards referred 

 to ; whereas there is nothing but the memory to fall back 

 upon in case of an erroneous record by the eye-and-ear 

 method. The amount of observing in a given time can be 

 nearly ten times as much, and with very little labor to the 

 observer. In cataloguing stars this becomes a great object. 



One clock is sufficient for any number of instruments ; and 

 in our Observatory we use the chronograph not only for the 

 transit but for prime, vertical, and other extra meridianal 

 observations, by leading wires from the observing circuit to 

 the different instruments used. Wires are also carried from 

 the Lighthouse, where, by means of a key, observations which 

 are being made for the astronomical ayzmuths of the different 

 trigonometrical stations can be directly recorded on the 

 chronographic paper, so that the otherwise troublesome and 

 often difficult determination becomes as easy and precise as 

 observations made in a fixed observatory. 



Considering the benefits derived from the adoption of 

 chronographic registration in our permanent observatory, I 



