May 20, 1875] 



NATURE 



45 



of lunar or solar hours (Mondbeziehungsweise Sonnen- 

 stunden) which have elapsed since the last upper culmi- 

 nation of either body respectively ; then the theoretical 

 elevation or depression of the sea in the Gulf of Fiume 

 due to these causes for any given time is found in milli- 

 metres by the expression :— 

 .. cos*5. 



+ 272-4 ^-s cos 



3 COS I (/„ - 8-49) 

 COS "S^ 



cos-^(/. 



;-57) 



+ 130-4 



-s COS — (4 

 12 



4-46) 



_^(/„- 4-60) + 60-3 



sin^25, 

 p. 



This is the" theoretical amount, not allowing for any 

 local retardation, or any'irfluence of the weather. 



The author has calculated this for a great variety of 

 conditions of the variable quantities, and compared them 

 with the results of observations, and the comparisons 

 have always been satisfactory. 



He gives comparative pairs of curves, one drawn by the 

 tide-gauge, the other calculated by the formula, and the 

 striking resemblance is at once appreciable by the eye- 

 The coincidence would be still nearer if the influence of 

 the small sidereal-time variations were added. 



The mean amplitudes of the four chief oscillations are 

 as follows : — 



Millimetres. 

 . 103-2 



55* 

 • 130-5 

 62-4 



For the oscillation of twelve lunar hours 



For that of twelve solar hours 



For that of twenty- four lunar hours 

 For that of twenty-four solar hours 



The maximum amplitudes are : — 



For the oscillation of twelve lunar hours ... 1 32 8 



For that of twelve solar hours 6o'9 



For that of twenty-four lunar houis 272*2 



For that of twenty-four solar hours ioo'2 



The author shows how the variable combinations of 

 these several elements determine and account for the 

 peculiar phenomena observed, and he explains in what 

 particulars the circumstances at Fiume would appear to 

 differ from those in other places, and to give rise to 

 special phenomena peculiar to that locality. 



He further devotes particular attention to the explana- 

 tion of the singular daily retardation, which he states has 

 also been noticed by M. Aimd on the coast of Algeria, 

 although it had been erroneously ascribed by him to the 

 effect of the wind. The real cause he shows to be the 

 oscillations depending on sidereal time. 



The non-periodical motions of the water are caused 

 chiefly by variations in the direction and force of the wind, 

 and in the barometer-pressure. The temperature of the sea 

 rain, and storms, may have also some influence, but too 

 slight to require investigation. 



The author therefore confines his attention to the wind 

 and the pressure of the air. In regard to the former, 

 looking at the form and position of the Gulf of Quarnero, 

 it is evident that southerly winds will force the water into 

 the cul-de-sac towards Fiume, and so will raise the 

 level, while northerly winds will tend to drive the water 

 out of the gulf, and £0 lower the surface. 



In regard to the barometer-pressure, it is pointed out 

 that if the weight of the atmosphere at any given part of 

 the sea differs from that at another part some distance 

 away, there must be a corresponding difference in the 

 level of the water ; [and this ^difference will be propor- 



tional to the specific gravities of the two fluids :— thus a 

 difference in the barometer of one inch of mercury will 

 cause a difference of level of about 13^ inches in the 

 water. 



The effects of these two influences are involved in 

 various complications, but they are sufficiently proved by 

 the records, and their amount is shown to be consider- 

 able. 



The following facts shown in the records will give some 

 general idea of the extent of the Mediterranean tides ; we 

 believe they are pretty much the same in all parts of the 

 sea. 



The highest water level known was on" Dec. 26, 1870, 

 being 0-870 metres above a certain datum point ; the 

 lowest was on Jan. 1 1, 1869, being 0-482 metres below the 

 same point. Hence the greatest difference of level 

 experienced was 1-352 metres, or>bout 4^ English feet. 



The average daily variation of level was 0*583 metres, 

 or nearly two feet English ; the greatest daily variation 

 was 0-825, and the least 0-259 metres. 



The mean daily variation of level is the same, what- 

 ever be the absolute general level of the water; as is 

 natural, seeing that the latter is influenced by local cir- 

 cumstances that have no effect on the attractions of the 

 sun and moon. 



The mean high and mean low water stand at equal 

 distances above and below the average mean level. 



The author modestly expresses the opinion that his 

 own three years' observations are of too limited extent to 

 determine fully the values of all the influences which affect 

 the tides, and he recommends that before the investigation 

 is carried further, accurate observations should be made 

 at other points of the Adriatic Sea, in order that, by a 

 combination of such data, the distinction between normal 

 and exceptional phenomena may be more positively 

 defined. No doubt such an extended inquiry would give 

 results of great value to physical science, and M, Stahl- 

 berger's excellent example is not unlikely to stimulate 

 others to co-operate in such an undertaking. 



The book is well got up. It is written in the national 

 language, but there is also given a translation into Ger- 

 man, and the data, in the form of tables, are so full and 

 complete as to enable anyone to verify, by his own 

 examination, the conclusions anived at by the author. 



OUR BOOK SHELF 



Cambridgeshire Geology j a Sketch for the use of Students. 

 By T. G. Bonney, F.G.S., Tutor and Lecturer in 

 Natural Science, St. John's College. Cambridge : 

 Deighton, Bell, and Co., 1875.) 

 Mr. Bonnev's short sketch of the geology of the neigh- 

 bourhood of Cambridge will be a useful handbook to 

 those students who wish to become practically acquainted 

 with the geological features of the country round their 

 temporary home. It makes no pretensions to be an 

 exhaustive description, and happily is not written in a 

 style suitable for cramming, but simply draws the atten- 

 tion of the careful reader to all the interesting points in 

 connection with the geology of the district, and notices 

 the various contributions to fact or theory made by pre- 

 vious writers, embodying many of Mr. Bonney's own 

 observations. The first deposits described are the Oxford 

 clay of St. Ives and the Elsworth rock, the true position 

 of which latter is discussed : and then follows a notice of 



