8 Art. 7.— S. Hirayaina. 



The approximate scale of the Thomson instruments is one 

 twentieth, and that of the Kobe one is of one twelfth. But more 

 exact scales are determined by comparing the readings of the wa- 

 ter outside and inside the cylinder. 



Sun-Dial. 



In general, the tide observatory is situated at a locality where 

 it is quite difficult to obtain the correct time, as the place is far 

 from a post-office or railway. A simple sun-dial is therefore pro- 

 vided for the clerk from the Land Survey Department, with a 

 table of the equation of time, which is so modified that, when we 

 apply the correction to the observed time, the central standard 

 time or the western standard time will be obtained. 



The sun-dial may be described as follows. A rectangular 

 piece of wood having parallel surfaces is taken, and on it a line is 

 marked. At one end of this line a vertical rod is fixed and the 

 other end of the horizontal line is connected with the upper ex- 

 tremity of this rod by a fine thread, so adjusted that the thread lies 

 in the plane defined by the horizontal line and a vertical line 

 erected at a point in the line. This instrument is used on a stand 

 made for the purpose ; it is a large stone having a plane surface. 

 The surface is carefully levelled and on it a meridian line is 

 marked. The clerk observes the transit of the sun over the 

 meridian with this instrument. 



The Duties of the Clerk. 



As the writer is informed, the clerk has the duty of visiting 

 the observatory twice in a day. He examines every part of the 

 instrument and whether the recording is going on without 

 hindrance. He takes the necessary care to put the instrument in 



