6o 



NATURE 



\Nov. 23, 1 87 1 



on the Physics of the Baltic ( ' ' Untersuchungen iiber Physikalische 

 Verhaltnisse des Westlichen Theiles der Ostsee") by Dr. H. A. 

 Meyer, of Kiel, containing the results of a continuous series of 

 mo-it careful and systematic observations on the temperature, 

 specific gravity, and movement of the difterent strata of its water, 

 dating back to the spring of 1S6S. Wuh this work I received a 

 letter from its author, of which the following extracts will, I think, 

 be interesting to your readers : — 



" I have followed with special attention the splendid results of 

 your different voyages, and hope that the experience which I 

 have gathered on a more confined area may yet offer something 

 which you may deem worth your attention. The favourable op- 

 portunity which I enjoyed fur continuing regular observations at 

 a spot where the wa'ers of the North Sea mingle with those of 

 the Baltic, enabled me to collect matters which cannot be brought 

 together on sea-voyages only ; and I should be much pleased to 

 see similar work undertaken at Gibraltar and Constantinople. 

 If among your large circle of acquaintance you might know of 

 gentlemen who may be interested in this cause, I should be 

 happy to send them my book. 



"I regularly read Nature, and am much surprised to find 

 that your views on Ocean-currents should not be universally ac- 

 cepted. How one can suppose that such a vast force which 

 constantly acts in one diiection should remain without any in- 

 fluence whatever, is perfectly incomprehensible to me ! 



" Most probably the cold under-current coming from the pole 

 will be — wherever it is not very confined — very slow ; but I 

 doubt not that, should you consider it of sufficient importance, 

 you will succeed in proving that the current, when confined, is 

 pretty fast, that is to say, fast enough to be measured by the in- 

 strument which you used in the Straits of Gibraltar. 



" With a similar appliance, which I have used for years, and 

 which you will find figured m my work, I have lately been able 

 to trace the heavier under-current in the Baltic to a much greater 

 distance. On board one of the despatch boats of the German 

 Navy, accompanied by some friends, I have this summer made 

 several trips through the Cattegat and Skager Rack, and into 

 the eastern parts of the Baltic ; and my views have been every- 

 where confirmed." 



I have further to state that my prediction that a similar under- 

 current of dense water must pass through the Dardanelles and 

 the Bo.sphorns from the /Egean into the Black Sea, which, it has 

 been alleged by Captain Spratt, is disproved by experiments 

 made by him several years ago, is regarded by three of the ablest 

 of our Hydrographers to be conclusively proved by those very 

 experiments when rightly interpreted. This I shall shortly 

 demonstrate in an appendix to the forthcoming Report of my 

 recent cruise. 



The case between Mr. CroU and myself, therefore, stands 

 thus : — 



1. I have experimentally proved the existence of an oulwanl 

 under-current in the Straits of Gibraltar, and have adopted the 

 gravitation theory of Captain Maury as affording an adequate 

 account of it. 



2. I have shown that this gravitation theory is applicable, 

 viutatis mutandis, to the converse cases of the Baltic and Black 

 Sea iincarJ under-currents, the existence of which has been ex- 

 perimentally demonstrated. 



I have further shown that it is applicable to that general Oceanic 

 Circulation, the evidence of which appears to me to be afforded 

 by the aggregate of observations that indicate the prevalence of 

 a temperature not far above 32° on the deep ocean-bottom, even 

 under the equator, and by the intermediate soundings which 

 indicate the existence of two distinct strata, separated by a 

 "stratum of intermixture," in parts of the deep ocean which the 

 Gulf Stream assuredly does not reach. 



These views have been accepted by Physicists of the highest 

 eminence ; but, as Mr. CroU affirms, without due consideration 

 of their theoretical difficulties. I venture to suggest, however, 

 that it is not beyond the range of possibility that Mr. CroU's data 

 may be erroneous ; and I do so with the more confidence, 

 because I have been assured by first-rate Mathematicians that the 

 science of Hydro-dynamics has not yet attained a development 

 which would justify the assertion, that (to use Dr. Meyer's words) 

 " a vast force constantly acting in one direction remains wuhout 

 any influence whatever." 



It happens that I very early became impressed with the power 

 of very small differences in Temperature to produce currents in 

 liquids, by tlie following remarkable fact, which has never (so 

 far as I am aware) been published. More than thirty years ago 

 Mr. West of Bristol (where I then resided) built an observatory 



on Clifton Down, the principal instrument of which was intended 

 to be a refracting telescope of large aperture, the object-glass of 

 which was to be made on the plan of Mr. Peter Barlow ; the 

 double concave of fiint being replaced by sulphuret of carbon, 

 or some other liquid of great dispersive power. The object- 

 glass was constructed with the greatest care, Mr. Barlow kindly 

 assisting in the computation of the requisite curves ; but when tried 

 it was found to be practically useless, in consequence of the 

 movement produced in the liquid by the very minute differences 

 of temperature occasioned by air-currents striking the surface of 

 the outer lens. 



I would also direct the attention of your readers to the 

 very interesting paper by Prof. Karl Mobius, the coadjutor 

 of Dr. Meyer, " On the Source of the Nourishment of the 

 Animals of the Deep Seas," of which a translation will be found 

 in the "Annals of Natural History" tor September. Care- 

 ful and prolonged observation of the movements of organic par- 

 ticles in aquaria satisfied him that very .shght changes of tem- 

 perature have a very important effect in prolucing changes in the 

 stratification, so to speak, of the water ; in one instance, he says, 

 " a downward current, which readily carried organic bodies along 

 with it, was produced when the difference between the superficial 

 and bottom temperatures had scarcely attained half a degree of 

 Reaumur (i°'i Fahr.)." 



Such being the facts of the case, and Mr. CroU having offered 

 no explanation of them, whilst demonstrating to his own satis- 

 faction that the explanation I advocate is untenable, I do not feel 

 called upon to discuss the subject further. There can be no 

 reasonable doubt that, within the next few years, a great mass of 

 additional data will be collected, which will afford adequate 

 materials for the construction of a definite Physical Theory, by 

 Mathematicians fully competent to the task. At present I do 

 not pretend to have done more than offer a hypothesis which 

 accords with the facts at present known, and with what Sir John 

 Herschel called the " common sense of the matter." 



Nov. 14 William B. Carpenter 



The Solar Parallax 



If Mr. Proctor had printed in full my memoranda on the 

 errors and imperfections of his history of the solar paraUax, or if 

 he had said nothing about it, I should have said nothing more in 

 defence of my review. But, in Nature of September 28, he 

 gives so inadequate an account of my notes, hiding the point of 

 the most remarUab'e of his inaccuracies, and ignoring the imper- 

 fections entirely, that I am compelled in self-defence to explain. 

 In describing the various discussions of the Transit of Venus 

 which preceded that of Mr. Stone, he says (p. 61) : " Newcomb, 

 of America, was more successful. He deduced the value 8" '87 

 by a method altogether more satisfactory than Powalky's. But 

 still the agreement between the difterent observations was not so 

 satisfactory as could be wished, nor had Newcomb adopted any 

 fixed rule for interpreting the obsei-vations of internal contact, 

 which, as I have said, are affected by the peculiar distortion 01 

 Venus's disc at that moment." 



To express my appreciation of this compliment it is only neces- 

 sary to say that I have no recollection of having discussed the 

 past transits of Venus at all, beyond correcting what I supposed 

 to be an oversight in Mr. Stone's paper, and I am still utterly at 

 a loss to know on what ground the compliment is based. In his 

 letter he tries to throw the responsibility upon an anonymous 

 correspondent of the Astronomical Register, which I regret to 

 say does not circulate here, but he does not quote anything to 

 justify a single statement in the preceding paragraph. The 

 correspondent says nothing about S' '87, which, it will be noted, 

 is Mr. Petrie's pyramid value, nor about my treatment of con- 

 tacts, so far as quoted by Mr. Proctor, so that I am as much in 

 the dark as ever. 



We have all heard suspicions that critics sometimes review 

 books without reading them, but this is the first time I remember 

 to have seen so circumstantial a description of a work which 

 never existed, save in the writer's imagination. I really cannot 

 help viewing it as something "remarkable" when coming from 

 a writer of Mr. Proctor's accuracy and erudition, and must beg 

 pardon if I measure his writings by too higi a standard. 



The imperfections consist briefly in the regularity with which 

 the more recent and complete researches on the solar paraUax are 

 ignored, incorrectly given, or placed in the back-ground of older 

 and less complete ones. If any one wants to satisfy himself of 

 this, he lias only to look at the papers and discussions which 

 have appeared in the Comptcs Rendus, the Monthly Notices, and 



