54 REPORT — 1876. 



executed ; then the final measurements for determination of zero, rating of clocks, 

 & c. were made, and the instrments started on their eighteen months' work. 

 Leaving Okha, the vessel in which I and my men and all the apparatus were in 

 ran straio-ht on to a sandbank and nearly capsized. After many troubles, the other 

 two stations were eventually constructed. Huts had to be made for the men in 

 charo-e and the guard from the native state to live in, a regular service for sending 

 food and water established, and post-runners started to carry the daily reports to 

 the nearest post-office, and many other details arranged. I or my European as- 

 sistant had to make frequent tours of inspection of the stations while work was 

 going on, which entailed much hard marching and exposure. One journey (in May 

 1874) was described in which I and my assistant had to ride on camels over about 

 fourteen miles of the Runn, covered with water from 6 inches to a foot deep, in 

 order to reach Haustal Tidal Station. The working of the stations was then de- 

 scribed, Okha and Haustal giving perfect and continuous registration ; but at 

 Nowanar, where there was 20 feet of water at the end of the pipe at low-water in 

 April 1874, in the following July it silted up and buried the pipe, and the whole 

 configuration of the foreshore altered. New pipes had to be got up, and two 

 lunations (from March to May 1875) were secured, in addition to the one and half 

 lunation got before the shore had altered, in 1874. The registrations of the ane- 

 mograph and barograph were continuous also. The levelling operations (750 miles 

 of double levelling were done in connexion with the work) were next noticed ; the 

 rigid method of procedure which obtains in the Great Trigonometrical Survey of 

 India, and which give such wonderfully accurate results, was referred to (vide Col. 

 Walker's paper in vol. xxxiii. of the Memoirs of the Astron. Society). 



The reductions of the tidal observations are in progi-ess, some idea of the magni- 

 tude of which may be imagined when 30,000 points have been con-ected to true 

 mean local time on the diagram-sheets, corrections made for zero error, and then 

 the 30,000 final measurements made and tabulated for reduction. The determina- 

 tion of the mean level of the sea at each station and some of the results already 

 deduced are stated : one is important, and that is, that the mean level deduced from 

 the two months (March 7 to May 7) is nearly identical with the mean of the whole 

 ear; and this Col. Walker had predicted would be the case in a letter on the subject 

 about eight years before. The meteorological reductions are in progress. The 

 movement of the wind for each hour for the whole period has been tabulated and 

 reduced to its N. and E. components, the mean hourly value determined ; and, by 

 combining the differences of this mean from the value of each particular hour, and 

 similarly the barometric differences with the differences of the theoretical and 

 actual values of the tide, I hope to determine far more accurately than has yet 

 been done the effect of the wind and barometer on the tide. Several tracings of 

 the actual diagrams were exhibited. The tidal curves are most regular and con- 

 tinuous, and show the perfect working of the whole apparatus ; and when the tidal 

 and meteorological reductions are complete, I hope to obtain some very valuable 

 results. 



Physical Explanation of the Mackerel Shy. 

 By Sir W. Thomson, D.C.L., F.B.S. 



On navigational Deep-sea Soundings in a Ship moving at High Speed. 

 By Sir W. Thomson, D.C.L., F.R.S. 



