/. Locke on the Electro- Chronograph. 245 



* 





of all at the same time, and the record will not only show sepa- 

 rately the work of each instrument, but if the observations be 

 interrupted by clouds or any other cause, as they frequently are, 

 it will show upon what wire in the telescope the star or other ob- 

 ject was at the time when the observation was made.* In view, 

 therefore, of the importance and practical value of this invention, 

 I consider that Dr. Locke has been as modest in his claims as he 

 is with regard to his own merits. 



18. The fifteen properties of the Chronograph contrasted with 



the three positive properties of the common magnetic clock, as 

 communicated to the Secretary of the Smithsonian Institution, 

 March, 1849, {in a letter to Prof Henry, from the author, dated 

 Washington, March 1, 1849.) 



I am anxious to have your opinion on the subject of my in- 

 vention, and I therefore put down some of its qualities as con- 

 trasted with those of other clocks : 



ORDINARY MAGNETIC CLOCKS 



1. Operate by interruptors or electrotomes. 



2. Cause electro-magnets to reciprocate at a distance. 



3. Impel other simpler clocks. 



4. Negatively, when the secondary clocks become retarded or 

 advanced by atmospheric electricity or otherwise, they will re- 

 main constantly in error until corrected by some external means. 



5. Negatively, their mechanism is such as renders it impossible 

 to use them for recording observations. See Art. 4 and 5. 



Dr. Locke's electro-chronograph 



1. Operates by interruptors or electrotomes. 



2. Causes electro-magnets to reciprocate at a distance. 



3. Impels other simpler clocks. 



4. Positively, when the electricity interferes with the current 

 in the wires, the time-scale, issued from the Morse Register, and 

 marked by my clock, though its evolutions may be temporarily 

 interfered with, yet as soon as the interfering cause is removed, 

 will issue in exact correspondence with the clock. 



The Morse Register may even be stopped and the graduating 

 of the scale be thus interrupted, yet when it is started again, it 

 will not recommence where it left off, but will indicate the then 

 time of the clock. 



5. The dial and hands remain on, and the clock can be used 

 for ordinary purposes by eye and car. 



* The part of the invention to which Lkrat Maury alludes m tint par raph, was 



onfidentially committed to him and has never been made in any degree pub he. In 

 this item the officers of the National Observatory itself are entitled to a share of 

 credit which will ultimately be distinctly accredited to the proper authority. 



