ON SEISMOLOtUCAL INVESTIGATIOX. 



:oo 



VIII. A Time Indicator. 



A slight moditication in the method of obtaining time marks on the 

 photogi'aphic him connected with the Milne Horizontal Pendulum is 

 shown in the accompanying sketch : — ■ 



Fig. 9. 



The watch, with its eclipse liand (see Report, 1897, p. 138), is replaced 

 by 'a small electromagnet whicli every hour, by a current lasting about 

 20 seconds, holds an eclipse plate over one end of the slit in the lid of the 

 box containing the clock driving the bromide him. The two wires con- 

 nect with two brass studs in the lower edge of the upper part of the film- 

 box, which tit into brass sockets in the upper edge of the lower half of the 

 .same box. From these sockets wires connect with the wheels on the two 

 sides of the box, the rails on wliich these run leading to a clock giving 

 the required length of contact. 



To get this length of contact the Shide arrangement is to prolong the 

 minute hand of a regulator with about ;| inch of platinum wire, which 

 every hour passes through a globule of mercury about the size of a pea, 

 standing iq) in a small insulated iron cup fitted in the brass frame which 

 carries the glass covering the clock face. The only advantage of this 

 arrangement is that it saves a little time in winding and comparing the 

 watch. Two platinum contacts rather than a platinum mercury contact 

 would be preferable. 



IX. On the Civil 'J'iine employed throur/Uout the World. 



With the kind assistance of the Foreign Office, the Colonial Office, and 

 the India Office, copies of the following letter have been circulated 

 thi-oughout the world. The text of the circular explains the object in 

 view. Numerous replies have been received from our Colonies, India 

 and its dependencies, but mitil these have been supplemented by replies 

 from many foreign countries the general report which it is desired to 

 draw up cannot be made. It is lioped that the necessary tabulation may 

 be undertaken for the Eeport for 18!)?. 



