1889.] Address. 79 



micrometer theodolite, by Troughton and Siinms, has been procured for 

 this work and it is intended to make the triangnlation as perfect as the 

 rest of India and to incorporate it therewith for the discussion of the 

 earth's figure. 



Tidal and Leveling operations. — The recording of the tidal curves by 

 the self-registering tide gauges, their reduction, and the publication of 

 the predicted heights have been continued as usual during the year at 

 18 stations round the coasts of India and Burma and at Aden. Work has 

 ceased at Negapatam, where 5 years' observations have been completed, 

 and at Elephant Point, where only 4| years' observations could be made, 

 owing to the observatory becoming unsafe. 



Two new observatories have been established, one at Tuticorin and 

 the other at the entrance to Princes' Dock, Bombay, where the gauge s 

 a new one by Lege and of a different pattern from any of the others in 

 use in India. An observatory will probably be started at Mergui at 

 once. 



The following summary of the results of the predictions for 1887 

 is interesting, as showing the comparative accuracy of predictions aud 

 actuals. 



Percentage of Predictions 

 within 15 minutes of actuals. within 8 inches in height of actuals. 

 High-Water. Low- Water. High-Water. Low-Water. 

 Open coast Stations 56 52 98 98 



Riverain ... 71 71 69 64 



In connection with the tidal operations, spirit-leveling operations 

 were carried out from Madras to Vizagapatam, via Nellore, Guntur 

 and Coconada, and from Chinsura to Nuddea, along the right bank of 

 the Hughli River. 



Tide tables for 1889 have been prepared which contain predictions 

 of the heights and times of high and low water for 28 ports, being one 

 more than in the volume for 1888. 



I may mention in connection with this subject that the first volume of 

 the Records of the Volcanic Eruption at Krakatoa, in 1883, lately 

 published by the Royal Society, contains the reductions by Captain 

 W. J. L. Wharton, R. N\, of the observations of the Seismic Sea 

 Waves, including those made by the automatic tide-gauges at different 

 points round the coast of India and at Aden, of which a report was 

 given by Major A. W. Baird, R. E., Survey of India, then in charge 

 of the Tidal operations. The observations have all been reduced to 

 Greenwich time, and show that the sea disturbance was probably com- 

 posed of two descriptions of waves, viz. : — long waves with periods of 

 over an hour, and shorter but higher waves with irregular and much 



