INSTRUMENT FOR TELLING THE HOUR IN THE DARK. 



fccutio the I think it preferable to a repeater, on account of its simpli- 

 "^ cit)' and cheapness. It is not liable to be out of oruer, and 



it does not require the exertion necesbary for pushing- the 

 pendant of a repeater, or disturb any person near it. 



Fevr these reasons 1 diffidently wish to have the honour 

 ©f laying this invention, which I call a Noctuary, befort the 

 Society ; and to be favoured with their decision on its msTits. 

 I am, sir, 

 Your respectful and obedient servant, 

 Elgin, March 7, 1810. GEORGE SPaRK. 



Reference to the JEngravinif of Mr. Spark's Noctnartj, 

 Pi,Yh Fig> 3, and 4, 



The apparatus A A, fig. 3, is a mahogany board, upon which two orhers, 

 nbtd, g ,^^^ Q^ g^j.g f^jjgjj^ gQ ag ^^ form a groove beneath and uu- 

 demeath them, in which the index D, shown separately at 

 fig» 4, descends.— Oh the opposite side of the board a flap 

 or door of mahogany is fixed by two hinges, a a, and a 

 clasp ; between this and the board A A a cavity is formed to 

 contain the watch, as shown by the dotted circle X ; the 

 diai appearing through a circle in the door, a hole is made 

 through the board A, opposite the fusee square, to rtceive 

 a key, upon which the small pulley E is tixed, and from 

 which the index D is suspended by a fine tiaead in the 

 groove above-mentioned. It is plain, that, as the fusee- 

 square and pulley E revolve, the index descends, and points 

 cut the hour by coming opposite the several marks, com- 

 mencing at nine and ending at seven, which are fixed upon 

 the board B ; the marks, from twelve to seven, are made by 

 pins projecting from the surface, so as to be readily distin- 

 guished by the finger; the index, represented in perspective 

 at L, fig. 4, is made very light, that it may not influence the 

 motion cf the watch. The watch must be wound up before 

 it is placed in the frame, and the thread wound up on the 

 pulley E, so much as to suspend the index nearly the 

 height of the hour when it is set; the key is then pushed on 

 the fusee-sqnai-e, and if the index does not point exactly at 

 the right hour, the jscale B can be slided up or down to ad- 

 Just it ; the screws dd, which hold it, being fitted m grooves 

 for this purpose ; after thi> setting, the index will point out 



any 



