J. Locke on the Electro- Chronograph. 243 



clock just now occurs. I am writing at night, the sky is very- 

 clear, and it is the first fair night for observations that we have 

 had this year. The wind is very high, and the observers have 

 just come in to say they cannot hear the clock, on that account, 

 and therefore they cannot observe. Now it is not necessary to 

 hear, or even to see the magnetic clock, and had we one, we 

 could work quite as well in windy as in calm weather. While, 

 therefore, one of Dr. Locke's magnetic clocks would be of such 

 value to the Observatory, it would, without at all interfering with 

 that value, be of incalculable advantage to the public generally; 

 for wherever in any part of the country there is a transit instru- 

 ment and a line of wires, this clock may be used by the observer at 

 that instrument, not only for recording his observations, but also 

 for determining his longitude from the capitol of the country ; and 

 thus it would without cost or trouble, enable the National Obser- 

 vatory to perform a most important part of appropriate duties, 

 and a most acceptable service to the world in perfecting the 

 geography of the country, and in affording so many well-deter- 

 mined points of departure for the traveller, the surveyor and the 

 navigator. 



17. The reply of Lieutenant Maury, Director of the Na- 

 tional Observatory, at Washington, to Senator Corwin, of Ohio, 

 {dated National Observatory, Washington, D. C, February 

 17, 1849.) 



I am this morning in receipt of yours of the 16th inst., in 



which you request my opinion as to "Dr. " 

 utility of his clock." 



I consider Dr. Locke's invention as one of the greatest im- 

 provements of the age, in practical astronomy. Other persons 

 have invented " Magnetic Clocks," but all those clocks, as far as 

 I know, beat seconds and leave the astronomer precisely where 

 he was before, as it regards the subdivisions of seconds. 



He had by them, as with other clocks, to trust to the eye and 

 the ear for the division of seconds. It was a great desideratum 

 with astronomers, and an important matter for the world, to ob- 

 tain the means of subdividing the seconds of time with accuracy 

 and certainty, for a second of time, in the determination of lon- 

 gitude, is equal to a quarter of a mile. . 



Dr. Locke took up this subject where others had left it and by 

 means of an attachment to a common clock, by the aid of electro- 

 maguetism and a common registering apparatus used in tele- 

 graphic offices, devised the means of subdividing accurately and 

 with precision, seconds of time into hundredths, or even into 



thousandths, if need be. „ . _, . M ' 



He has chosen to call iiis invention a "Magnetic Clock. I 

 think that is rather a misnomer ; for a clock to be driven by mag- 



Locke 



