44 



NATURE 



\May 20, 1875 



strait of a few miles in width, this inland sheet of water 

 is so effectually shut off from the general tidal move- 

 ments of the main ocean, that it has often been called a 

 " tideless sea." But this is not correct ; for, having an 

 extent of surface of some 700,000 or 800,000 square miles, 

 it is sufficiently large to be itself specially affected by the 

 attraction of the sun and moon, and thus it possesses a 

 true, although small, tide of its own. 



The daily variations in the level of the water have of 

 course been always patent to the dwellers on the Medi- 

 terranean coasts ; and, no doubt, careful observers must 

 have remarked a periodicity in the recurrence of such 

 variations, identifying them to a certain extent with the 

 ocean tides. But from the small amount of the true 

 periodical rise and fall, and from the large influence of 

 accidental causes, the phenomena have been so irregular 

 as to present great difficulties in their analysis ; and, so 

 far as we know, there has not been, down to the appear- 

 ance of the present work, any systematic investigation of 

 the subject put on record. 



The present publication has arisen from a prize of 200/, 

 having been offered in 1872 by the Royal Hungarian 

 Society (from funds furnished by Government) for scien- 

 tific labours bearing on the physical or meteorological 

 conditions of the kingdom of Hungary. 



Fiume is a town of some importance, lying on what is 

 called the Hungarian littorale, washed by the waters of 

 the Gulf of Quarnero, an irrregular-shaped recess in the 

 extreme north-eastern part of the Adriatic. The Govern- 

 ment of Hungary, desirous to promote the maritime inte- 

 rests attached to their little seaport, have established 

 there a Marine Academy, and M. Stahlberger, one of the 

 professors in that institution, had had occasion to make 

 and register observations on the rise and fall of the 

 water in the neighbouring roadstead. Conceiving that 

 by studious labour the phenomena he had recorded might 

 be reduced to something like rule and order, he under- 

 took the elaborate theoretical discussion of them, and 

 the Society, appreciating the value of the work, has not 

 only awarded him the prize for it, but has published it, 

 in full detail, for the benefit of science in general. 



The author was led to this investigation by the double 

 object of obtaining accurate information, first, as to the 

 general phenomena of the tides in the Adriatic, or rather 

 in the Mediterranean generally ; and secondly, as to the 

 peculiarities in these phenomena induced by local influ- 

 ences in the neighbourhood of the port of Fiume. 



He remarks, in regard to the first point, that the semi- 

 mensual irregularity which it is customary to deduce from 

 observations, in order to predict the times of high and low 

 water, is altogether different in the Adriatic from what 

 obtains in regard to the ocean generally; and yet the 

 causes of this difference have never yet been explained. 



In regard to the second point, he refers to notices that 

 had appeared of remarkable irregularities in the Fiume 

 tides, which rendered further investigation very desirable. 

 It had been perceived, that instead of the usual six hours' 

 alternating ebb and flow, there was frequently only one 

 high and one low water in the day ; and, moreover, that 

 the time of the lowest water advanced on the average two 

 hours every month, or twenty-four hours in a year. 



These strange phenomena had attracted attention, and 

 in 1868 the Adria Commission of the Imperial Academy 



of Sciences at Vienna established a self-registering tide- 

 gauge at Fiume, the control of which was entrusted to 

 M. Stahlberger. The present essay contains the results 

 of three years' observations, which are fully and scientifi- 

 cally discussed by him. 



The tide-gauge was on a plan that has often been used 

 in this country. It consisted of a float, which by means of 

 connecting machinery and a pencil made a mark on a 

 sheet of paper stretched on a drum. The drum being 

 moved uniformly by clockwork so as to make one revolu- 

 tion in twenty-four hours,' the height of the tide at any 

 time of the day could be deduced by simple measurement 

 from the curve produced on the paper. The same paper 

 was used for three days' observations, the curves being 

 distinguished from each other by different coloured 

 pencils being attached at the beginning of each day. 



The author appears to have gone to work in his investi- 

 gation in a thoroughly philosophical way. He has first 

 collected a very large number of facts, as shown by the 

 records of his gauge ; he has then tabulated them with 

 great carejand ingenuity, classifyingj^them with special 

 reference to the nature of the influences known to be in 

 operation, such as the positions of the heavenly bodies, 

 the direction and force of the wind, the state of the baro- 

 meter, and so on ; and finally, working on the records 

 thus arranged, he has, by applying scientific calculations 

 of a high order, been able to a large extent to simplify 

 the complicated questions involved, and to throw much 

 light on their explanation. 



To facilitate the investigation, he divides the tidal 

 phenomena into two classes : namely, in the first place, 

 periodical motions of the water produced by cosmical 

 causes ; and secondly, non-periodical motions produced 

 by the influence of meteorological or local agencies. He 

 then discusses each of these two divisions at considerable 

 length. 



As to the periodical motions, he found that in calm 

 weather, and even to a less extent at unsettled times, the 

 figures drawn by the gauge showed unmistakable signs 

 of periodicity ; but the appearances were of two kinds : 

 sometimes they showed two well-defiued maxima and 

 minima, six hours apart ; at other times there was only 

 a single maximum and minimum, sharply defined, these 

 two types melting into each other with all gradations. 



These regular forms were clearly to be referred to the 

 periodical motions of the heavenly bodies, and the author, 

 having carefully collected and arranged the facts, enters 

 into a long and full theoretical discussion of their causes, 

 according to the principles laid down by Newton and 

 Laplace. 



We cannot pretend to give any details of the laborious 

 mathematical calculations which follow : it must suffice to 

 extract the author's brief summaryof his results on this 

 head. He says that the periodical movements of the 

 sea in the Gulf of Fiume depend in the first place on 

 four simple oscillations, two of the sun and two of the 

 moon ; and secondly, on four other simple vibrations, 

 two due to each body, which are reckoned in sidereal 

 time, but which have only a slight effect, and may be 

 neglected in computation. 



If 8,„ and S^ represent the declinations of the moon and 

 sun respectively, p^ and p their distances (expressed in terms 

 of their respective mean distances), /„ and /^ the numb 



