On the Application of Galvanic Electricity, b^c. 145 



Art. VII — On the Application of Galvanic Electricity to 

 Practical Astronomy . Tly li. J. L. Ellery, Esq., Govern- 

 mcut Astronomer. 



[Read before the Royal Society, August 27, I860.] 



The application of electro-dynamics to astronomical purposes 

 presents one of the most marked featiu'es in the history of 

 modern astronomy ; and it is probable that without the 

 assistance of the electric current, no improvements that could 

 be devised in the optical construction of the instruments used 

 Avould secure the almost absolute precision Ave can noAv attain 

 in those observations in Avhich the accurate determination of 

 time is of primary importance. 



The application of electro- dynamics, styled indifferently 

 chronof/raphy and galvanic registration, has resiilted in such 

 decided advantages in the great American and Eui'opean ob- 

 servatories, into most of which it has been introduced, that 

 no observatory of any pretensions can be considered complete 

 without it. 



The aim of my paper this evening is not so much to enter 

 upon the history and successive improvements made in this 

 application of electricity, as to describe to the society the 

 maimer in which it has been adopted in the Astronomical 

 Observatory of this colony, and especially to call attention to 

 a recently constructed chronographic apparatus, which Avill 

 be of great assistance in making the astronomical observa- 

 tions in coiniection with the geodetic sui'vey. 



The first use of the galvanic current in astronomical ob- 

 serving was made by Professor Locke, of the United States, 

 as early as 1849, and although its successive adoption in 

 various observatories has led to many improvements and 

 modifications of tlic original mechanical arrangements, the 

 principle remains the same. The general form of the appa- 

 ratus may be described as consisting of an electro-telegraphic 

 register, Avith a double system of electro magnets and indent- 

 ing styles, each system liaA-ing a separate galvanic circuit. 



Tlie chronographic apparatus noAV in use at the Astro- 

 nomical Observatory may be thus described : — 



The register, Avith the exception of its possessing a double 



L 



