January 12, 1899] 



NATURE 



247 



things as orbits, but that the planets sweep on through a 

 pathless void, in directions perpetually changed by gravitation." 

 It remains to remove a misapprehension of Prof. Meldola's 

 own. He says : " It may be well to indicate that many — per- 

 haps we may say the majority of biologists in this country — 

 have long ago parted company from Mr. Spencer on this ques- 

 tion of the enhanced importance of ' direct equilibration,' and 

 the subordinate position assigned to ' indirect equilibration ' in 

 his later writings." I know of no foundation for such part of 

 this statement as refers to my opinions. That I have not 



■ changed my view concerning the respective shares of direct and in- 

 direct equilibration there is incontestable proof. If Prof. Meldola 

 will turn to § 170 (p. 46S) of the " Principles of Biology," first 

 edition, he will find it there contended that at first "natural 

 selection worked almost alone in moulding and re-moulding 

 organisms into fitness for their changing environments ; and 

 natural selection has remained almost the sole agency by which 

 plants and inferior orders of animals have been modified and 

 developed." He will find it further said that in proportion as 

 organisms become comple.x and active, "the production of 

 adaptations by direct equilibration takes the first place — in- 



■ direct equilibration serving to facilitate it." And now, if he will 

 turn to the revised edition of the "Principles of Biology" 

 issued last year, he will find that the two sentences quoted stand 

 as they did in 1864. 



Prof. Meldola has been misled by a not unnatural illusion. I 

 have of late years had occasion frequently to insist on the share 

 taken in organic evolution by direct equilibration (or the 

 inheritance of functionally-produced changes) because it has 

 been continually denied ; and frequent insistence on its share has 

 been mistaken for an alleged extension of its share. 



Brighton, January 8. Herbert Spencer. 



Carte Geologique internationale de I'Europe. 



I have just received, through Mr. Edward Stanford, 

 Livraison iii., containing seven sheets of this great work, in 

 which we have the maps of the British Isles, of Germany, Italy, 

 Austro-Hungary and Greece. These maps exhibit a marvellous 

 amount of care on the part of the Directors, and of elaborate 

 execution on the part of Herr Dietrich Reimer and his staff. I 

 do not venture to eulogise, much less to criticise the maps, but 

 only to direct attention to one special point of interest which 

 they exhibit, namely, the representation of the great terminal 

 moraines on both sides of the Alps. It requires a little close 

 scrutiny to discover the course of these great banks of glacier 

 detritus laid down at the epoch of greatest cold of the Glacial 

 Period ; but once recognised, it amply repays attention to follow 

 their course. They are represented by lines of purple dots, 

 about three or four deep, lessening in size inwards ; and, of 

 course, passing disconnectedly over all the geological formations. 

 On the north base of the Alps the moraine bank starts from 

 above Grenoble, swelling northwards near to Lyon along the 

 Rhone valley ; then, retreating southwards, it winds along the 

 flanks of the Jura above the plain of Geneva and Lake Neu- 

 chatel ; then passing by Berne and Ziirich, stretches away 

 northwards by Schaffhausen and Ravensburg, indicating the 

 enormous extent of the old Rhein Glacier; and then curving 

 outwards along the valleys descending from the eastern Alps by 

 Munich and Salzburg, it is represented as surrounding the 

 northern shore of the Traun See ; but no further eastwards. 



The northern limit of erratic blocks is represented by a nearly 

 continuous red line extending generally much further from the 

 base of the Alps than is the case with the terminal moraines. 

 Commencing on the west at Grenoble the line curves round by 

 Lyon and Bourg, and then ranging along the Jura Meridional, 

 celebrated for the huge boulders of granite which are there 

 stranded, stretches northwards towards Besancon ; thence, 

 skirting the Rhein valley near Basel, the line stretches eastward 

 by Schaffhausen, where it almost skirts the northern base of the 

 moraine, and so passes onwards by Munich to the banks of the 

 Enns by Steyr (Steyer). 



The great glaciers which descended from the Alps on the 

 Italian side have (as is well known) left behind them huge 

 moraines, which are also represented in a manner similar to those 

 on the north side. Thus we have the great terminal moraines 

 of the rivers Dorea Riparia and Dorea Baltea near Turin ; 

 then, further eastward, those which border the southern shores 

 of Lakes Maggiore, Como, D'Iseq and Garda. The southern 

 limit of erratics is only represented at a few places, and then 



NO. 1524, VOL. 59] 



generally in close proximity to the margin of the moraines. 

 The close connection of the great Italian lakes with the moraines 

 cannot be overlooked by those who recognise the evidence 

 adduced by the late Sir A. C. Ramsay in support of his views 

 on the glacial origin of lakes. The moraines of the Dorea 

 Riparia and Dorea Baltea were amongst his favourite illustra- 

 tions. 



Before closing I might be allowed to add that the topography 

 of the map is admirable, while the coloration of the geological 

 formations, except, perhaps, in the case of the British Isles, 

 fully sustains the reputation of the Lithographic Institute of 

 Berlin. Edward Hull. 



January 3. 



Periodic Tides. 



Capt. a. S. Thomso.n (p. 125) calls attention in your columns 

 to the subject of short period oscillation of water-level at Malta 

 and Sydney, and asks for further information from others. As 

 I have given some attention to studying similar phenomena on 

 the eastern coast of Canada, I venture to offer the following 

 additional information and suggestion of an explanation. 



(i) The phenomena are very common. At St. John, New 

 Brunswick, on the coast of the B.iy of Fundy, the oscillations 

 have a fairly constant period of 43 minutes. At Quaco, a few 

 miles further up the bay, the period is only izh minutes. At 

 Halifax, Nova Scotia, on the Atlantic coast, the period is 23^ 

 minutes. In the Gulf of St. Lawrence, at South-West Point 

 (Anticosti), the oscillations are rapid but irregular; at St. 

 Paul's Island, very rapid and irregular ; at Forteau Bay, small 

 and irregular ; at Carleton ((Quebec) there is some indication of 

 a22-minute period ; at Souris (Prince Edward Island) the oscil- 

 lations are rapid and irregular ; at Pictou (Nova Scotia), small 

 and irregular : at St. Peter's Island, very rapid and irregular. 



(2) Any explanation must account for two distinct things : 

 the origin of the fluctuations, and their periodicity. Let us take 

 these in reverse order. 



(3) The period of the oscillations (where they have a definite 

 period) is, I believe, simply the period of the free natural 

 vibrations of a semi-confined body of water " wish-washing " 

 to and fro like water in a wash-bowl, the oscillations being 

 sometimes fiindanicntal — that is, consisting in the vibration of 

 the body of water as a whole ; and in other cases (perhaps the 

 majority of cases) partial — that is, due to the body of water 

 dividing up into two vibrating halves, or three-thirds, &c. In a 

 very irregular basin, like the Gulf of St. Lawrence, regular 

 vibrations are impossible. In some other cases the basin is of 

 sufficiently regular form to admit of fairly regular oscillations, 

 but not regular enough for the period to be deduced mathe- 

 matically. In only two cases have I found a mathematical test 

 possible. At St. John, the Bay of Fundy is bounded on one 

 side by the slightly indented New Brunswick coast, and on the 

 other side by the straight, abrupt Nova Scotia coast, these two 

 shores being only slightly inclined to one another. The width 

 may be taken as forty miles, and a study of the chart gives the 

 mean depth al low tide as 34 '4 fathoms. The period of fund- 

 amental vibrations across such a basin is given (to a sufficient 

 approximation) by 



/ being the width, and h the mean depth. With the above 

 figures, this gives for fundamental vibrations a period of 87 

 minutes, and for first partial vibrations a period of 43'5 minutes. 

 The latter is remarkably close to the observed period of 43 

 minutes. It should be noted that the calculation applies to low 

 tide. Now, the tide at St. John has a range of 20 feet, while 

 the formula shows that the period vaiies inversely as the square 

 root of the mean depth. A simple calculation shows that the 

 period at high tide should be two minutes less. From an exam- 

 ination of all the cases avail.able, I found that the mean period 

 for high tide was actually i'6 minutes shorter than for low tide ; 

 but the fewness of the well-marked cases available to me for 

 making this te.st (thirteen in all) makes me believe that this 

 agreement is somewhat accidental. 



The other case known to me to which a similar calculation 

 can be applied, is that of a small basin in the St. John River, just 

 before it flows through a very narrow gorge into the harbour. 

 While using a rough form of self-recording tide gauge for find- 

 ing accurately the time of high water, I discovered on the 



