Oct. ii, 1888] 



NATURE 



569 



Lord Alcester assures me that there was no doubt of 

 the breakers, otherwise it might be thought that the 

 deceptive appearance that misled Captain Aldrich, also 

 misled the officers of the Pelorus. 



It thus appears probable that, as in some other cases 

 (of which the Graham Island in the Mediterranean is 

 perhaps best known), the cinders and ashes which formed, 

 and still form, the summit of the volcanic mound origin- 

 ally thrown up, are being by wave-action gradually swept 

 away, and will continue to be so removed until the top of 

 the bank is reduced below the limit of such action, or, as 

 in the case of the Graham Shoal, the solid rock is laid 

 bare. 



If so, it is another case of the preparation of a suitable 

 foundation for coral builders by a process directly the 

 reverse of that of building up by marine organisms on 

 mounds that have failed to reach the surface, suggested 

 by Mr. John Murray to be the principal method. 



It remains for those who have made submarine erup- 

 tions their study to say whether a mound raised in the 

 sea is covered with loose matter in a sufficient percentage 

 of cases to justify this mode of coral-foundation-making 

 being given an important place amongst others. 



In the latest known cases of islands so formed, viz. 

 Steers and Calmeyer Islands, thrown up near Krakatab in 

 1883, and Falcon Island, which appeared in 1885 in the 

 Tonga Group, the surface structure was loose. The two 

 former very shortly disappeared below the level of the sea. 

 What is happening to the latter is not known, as it is 

 seldom sighted; but 1 from its volume and height (290 

 feet) the process of reduction, even if no compact nucleus 

 exists above water, must be slow. 



The deceptive appearance of the masses of minute 

 organisms which floated in the vicinity of the bank is no 

 doubt an abundant source of false reports. These clouds 

 of matter are commoner in inclosed and calmer waters, 

 like the Red Sea, than in open oceans, where they are so 

 much more liable to be dispersed by the waves before 

 they can accumulate to any size. The assistance they 

 afforded in this instance to the searchers is remarkable, 

 and so far as I know unique, as they are generally found 

 in deep water. W. J. L. Wharton. 



RECENT VISIT OF NATURALISTS TO THE 

 GALAPAGOS. 



CAPTAIN J. M. DOW has placed at my disposal 

 the subjoined short account of a visit recently paid 

 to the Galapagos Group by the United States steamer 

 Albatross, which will, I am sure, be of much interest to 

 naturalists. P. L. Sc later. 



U.S. Commission of Fish and Fisheries, 



Steamer " Albatross" Acapulco, Mexico, 



April 24, 1888. 

 Captain J. M. Dow, Panama. 



My Dear Sir,— Thinking that you might like to know 

 something of the results of our trip to the Galapagos, I 

 take this opportunity of writing. 



Leaving Panama on the morning of March 30, we made 

 during that day six hauls of the trawl in depths from 

 7 to 51 fathoms. These gave us fine results, including 

 many species with which you are doubtless familiar. 

 The fishes included species of Upeneis, Arius, Poly- 

 nemus, Aphronitia, Serranus, Selene, Prionotus, Hamil- 

 ton, Synodus, Tetrodon, Ophidium, Scicena, Micropogon, 

 Lophius. We were delighted to see Thalasophryne 

 and two allied species. The number of shells, Crus- 

 tacea, &c, was almost innumerable. The care of so 

 much material kept us very busy. The next day we 

 sounded off Cape Mala, and found the depth to be 1927 

 fathoms. No more dredging was done until we neared 

 the Galapagos on,April 3, when we made a haul in 1 379 



fathoms, where the amount of material obtained was 

 small, although it included some very good things. At 

 the islands we made visits to eight of the principal ones, 

 Most of our days were spent on shore, beginning early in 

 the morning, and oftentimes bird-skinning and other work 

 was prolonged far into the night. The islands presented a 

 very inhospitable look along the shores, with the black 

 lava cropping about everywhere ; but in two of them 

 (Chatham Island and Charles Island) the interior was 

 extremely fertile and pleasant. Collecting was always 

 difficult ; but, with the co-operation of officers and men, 

 we obtained a great quantity of material. We naturally 

 looked to the birds first, on account of Darwin's previous 

 work there. We have over 250 good bird-skins, besides 

 several hundred specimens in alcohol, and a few skeletons. 

 Of the fifty-seven species before reported from there, we 

 obtained examples of fifty or more, and we have, in 

 addition, several which are apparently new to science. 

 We hope, with our material, to settle some of the curious 

 problems of these islands. 



We secured specimens of all the reptiles which have 

 been before found there, and also hope that we have two 

 or three new lizards. The tortoises excited great interest, 

 and it would please you to see the many large ones which 

 are now crawling about our decks. We expect now that 

 we shall be able to raise them in the States. 



Fishing was good at all of our anchorages, and we all 

 had sport in catching fishes over the ship's side. We 

 got between thirty and forty species in all, including a 

 large brown " grouper," which is there caught and salted 

 for the Ecuador market. 



One night, while running from one island to another, 

 we stopped and drifted for a while, and put the electric 

 light over the side. Besides many small things, large 

 sharks came around in great numbers. More than twenty 

 were seen at once, and I know that the sight would have 

 pleased you. We all regretted that you were not with 

 us. Notwithstanding the necessity for rapid work, good- 

 fellowship always prevailed as usual. I hope that some 

 time you may take a trip with me on the Albatross, and 

 see how we do it. 



Hoping that this will not prove too long an account for 

 you, 



I remain, 



Yours very sincerely, 



Leslie A. Lee. 



THE BRITISH ASSOCIATION. 



Section A — Mathematical and Physical Science. 



A Simple Hypothesis for Electro-magnetic Induction of In- 

 complete Circuits ; with Consequent Equations of Electric 

 Motion in Fixed Homogeneous or Heterogeneous Solid Matter, 

 by Sir William Thomson. 



(1) To avoid mathematical formulas till needed for calculation 

 consider three cases of liquid l motion which for brevity I call 

 Primary, Secondary, Tertiary, defined as follows : — Half the 

 velocity in the Secondary agrees numerically and directionally 

 with the magnitude and axis of the molecular spin at the 

 corresponding point of the Primary ; or (short, but complete, 

 statement) the half velocity in the Secondary is the spin in the 

 Primary, and (similarly) half the velocity in the Tertiary is the 

 spin in the Secondary. 



(2) In the Secondary and Tertiary the motion is essentially 

 without change of density, and in each of them we naturally, 

 therefore, take an incompressible fluid as the substance. The 

 motion in the Primary we arbitrarily restrict by taking its fluid 

 also as incompressible. 



(3) Helmholtz first solved the problem — Given the spin in 

 any case of liquid motion, to find the motion. His solution 

 consists in finding the potentials of three ideal distributions of 

 gravitational matter having densities respectively equal to 1/4/ir 

 of the rectangular components of the given spin ; and, regarding 



1 I use " liquid " for brevity to signify incompressible fluid. 



