6 REPORT 1844. 



observers had found it impossible to comply with the instructions which had been 

 furnished to them, for it was found impossible to fix upon any of the apparently 

 lawless elevations and depressions of the water as representing the usual semi-diurnal 

 high water or low water. The result was, that of themselves they adopted the 

 prudent course of giving up any attempt at such selection, and observed the height 

 of the tide every five minutes throughout the twenty-four hours. This was a fortu- 

 nate circumstance, for in consequence of being in possession of these almost con- 

 tinuous observations for such a period, he had been able to make out the law ; which 

 under other circumstances might have long continued to perplex. It was found that 

 semi-diurnal tides very small in their actual amount, sometimes not more than a few 

 inches, succeeded each other at irregular intervals ; and this was very clearly traced to 

 the influence of the relatively large amount of the solar tide,which, upon examination, 

 was found to be distinctly larger than the lunar tide. With this was mingled a di- 

 urnal tide, as large as the diurnal tide at the neighbouring parts of the coast ; and also 

 a quarto-diurnal tide, which is found to exist on nearly every part of the coast, and 

 which has its largest value at or near Courtown. The Astronomer Royal said that 

 he was preparing a detailed account of these observations ; and he closed by saying, 

 that in reference to the object for which they had been chiefly undertaken, it was 

 now obvious that no fixed plane sufficiently determinate for engineering purposes could 

 be deduced from the phaenomena of the tides ; at least those observed on the coast 

 of our island or of continental seas. 



On the Tides of the East Coast of Scotland. By 3. Scott Russeli,, F.Ii.S.E. 



The discussion of the* observations was now complete, and they were ready for 

 publication. The chief part of the results had been reported last year, but there re- 

 mained a few interesting points which had been brought out by the recent discus- 

 sions. The chief of these was the determination of the diurnal inequality in the time 

 of high water, a phaenomenon which, as stated by Sir J. Lubbock, has not been dis- 

 covered on our coasts. This inequality had been manifested in a very prominent form 

 in these observations on the east coast of Scotland ; and diagrams were exhibited, in 

 which not only its existence was marked, but its magnitude was measured, and was 

 so great, that the time of high water of successive tides varied, with 25° of declina- 

 tion, as much as from 30 to 80 minutes from this cause. Tables were also given, 

 showing its amount in various ports along the coast. He attributed the detection of 

 this inequality, which had hitherto escaped notice, to the methods of observation 

 which had been employed. His system was to employ, instead of the mere obser- 

 vation of the height and time of still water, or the cessation of rise and the commence- 

 ment of fall, a continuous series of observations every five minutes on time and 

 height. This series was registered continuously night and day, and the observations 

 were all laid down on ruled paper in a wave cun'e, from which the observations of 

 time and height were deduced. It was the accuracy of the system of discussing in- 

 dividual wave curves, instead of mere observations of height and time, which had 

 enabled him to detect phjenomena that had formerly escaped observation ; and he 

 was glad to find that Professor Airy had recommended and adopted that method in 

 his recent observations on the tides of Ireland. Another advantage which the method 

 of observation and discussion of individual wave curves produced, was that tolerably 

 correct tables, for the prediction of tides, might be formed from a very short series 

 of observations. He had found Sir J. Lubbock's tables of the tides of Leith, deduced 

 from many thousand observations, to be very accurate ; and from them the tides of 

 Leith were predicted so as to coincide exactly with the phaenomena. But, by the 

 method of observation now mentioned, he had formed tables from a few weeks' ob- 

 servation, which coincided quite as accurately with Sir J. Lubbock's tables as those with 

 obser\'ation. He concluded by noticing an ingenious Self-Registering Tide-Gauge, 

 invented by Mr. Wood of Port Glasgow, which was so simple as to be constructed 

 to register heights at a cost of two or three pounds, and to register time at a cost of 

 ten pounds. He was happy to add, that tide-gauges of this kind were now being 

 erected at Cork. 



