21 6 Substitute for a Repeating Watch. 



Table of Correction. 



23-p 



Declination] O'M 3= 6 



Correction. [0"-00|0"-] 2 



15" 18° 



0"-24 0"36b"49'0' 62 0"-75 



21° 



■88 



1"00 



One example will make the whole intelligible to the 

 meanest capacity. 



Suppose it was required to correct the sun's declination 

 as given m the Ephenieris when at 15°. 



Under 15° you have o''*62, being the correction 

 for l" of difference. 



As the error or difference 'I . „ 

 is 8" loo little. Multiply / 



4'"- 96 to be added to the de- 

 clination as found in the Ephemeris, and this will be the 

 true declination nearly. 



Yours, &c. 



March 3, 1812. JJ_ Y. P. 



XXXII. Substitute for a Repeating Watch. 



To Mr. Tilloch. 



Sir, jL he common watch, which is so extremely useful 

 in the day, is of very little use in the dark. To remove this 

 imperfection, a watch was invented which repeats the hour 

 and quarters at any time of the day or night. Watches of 

 this construction are exceedingly convenient, but they are 

 too expensive for generj^I use; and all other instruments 

 contrived to answer the same purpose, that have come 

 under my inspection, though less expensive are less con- 

 venient. 



After many unsuccessful attempts to construct an in- 

 strument to supply the place of a repeating watch, at a 

 small expense, and that might be equally useful, 1 found that 

 a common watch with a very little alteration would answer 

 the purpose perfectly well. 



To make a conniion watch into a nocturnal one, I made 

 notches with a file in the rim of its inner case, against every 

 hour upon the dial, except 3, 6, 9, and 12. These tangible 

 marks are made no deeper than just to receive the nail of 

 the finger or thumb, as it is drawn over them. The hour 

 of 12 is known by the pendant, and little pins are fixed int© 

 the case at the hours of 3, 6, and 9, projecting outwatds 



about 



