153 On the Application of Galvanic Electricity, S^c. 



ment of the waggon is regulated by the clock-work, and 

 during the working of the apparatus it progresses on the rail 

 about a quarter of an inch for every revolution of the barrel. 



In using the apparatus, the drum has to be covered with a 

 proper sheet of paper, which is fitted on damp, the joining 

 edges being gummed together with isinglass. To do this 

 conveniently, the drum is made so that it can be removed 

 from its bearings very readily. When the paper is dry, and 

 all the connections and adjustments made perfect, the instru- 

 ment is ready for use. On setting the train in motion, the 

 drum will revolve slowly and uniformly on its axis, and the 

 waggon, with its electro-magnets and styles, also moves in the 

 direction of the barrel axis. The two circuits are similar to 

 those in the Observatory, and require no further explanation. 



One style punctures the seconds transmitted by the chro- 

 nometer circuit, the other punctures the observation record ; 

 and the two sets of punctures are distinguished by their size. 

 The relative motions of the drum and waggon causes the two 

 series of punctures to assume the form of a spiral line around 

 the cylinder. In order that the styles may not stop the 

 cylinder, if they happen to remain in the paper for a longer 

 time than is required, they are allowed to follow the motion 

 of the cylinder a little, but when they are withdrawn from 

 the paper, by means of a spring, they immediately resume 

 their proper position. 



The reading off is performed in a similar manner to that 

 of the fillet register, but it is necessary to remove the paper 

 from the cylinder before this can be done. 



In conclusion, I would remark that there is nothing ori- 

 ginal in the chronographs used at the Observatory, the clock 

 contact being very similar to the one used at Greenwich, and 

 the register is of the most usual form. The portable chro- 

 nograph, as far as the register is concerned, is a modification 

 of one lately made for the Altona Observatory, the chro- 

 nometer contact being the only portion which, I believe, has 

 any claim to originality. 



