328 



HISTORY OF ASTKONOMY. 



I 



to trace a spiral on the cylinder, and one sheet of paper, 

 twelve inches by twenty, lasts for more than two hours 

 of constant work. Two sheets will contain 

 an ordinary night's work. 



In order to secure the full advantage of 

 this method, it is important that the paper 

 which contains the register be made to ad- 



, s vance with entire uniformity. The Messrs. 

 Bond have invented for this purpose a 



^ machine which they call the Spring Gov- 

 ernor, consisting of a train of clock-work 



^ connected with the axis of a . fly-wheel. It 



H has an escapement-wheel, into the teeth of 

 which pallets are operated by the oscillations 



5> of a pendulum, as in ordinary clocks, the 

 wheel being so connected with its axis by 

 a spring as to allow the axis to move while 



^ the wheel is detained by the pallets. The 

 register is made upon a sheet of paper 



*> wrapped round a cylinder. The annexed 



% specimen is a fac-simile, taken from a record 

 sheet used at the Cambridge observatory. 



^ A B shows the signal announcing the ap- 

 proach of a star to the right ascension wires 



* of the transit instrument; C indicates the 



passage of the star over the first wire ; and 

 D-indicates the passage over the second wire 



o The passage over the first wire took 

 place at 7h. 16m. 7s.4, and the passage 

 over the second wire at 7h. 16m. 11s. 4. 





