Dec. 4, 1879] 



NATURE 



107 



it so happens that I was present, and can testify to the accuracy 

 of Mr. Mello's statement. With regard to the tooth of Macbai- 

 rodus, which I discovered and afterwards showed to Mr. Heath, 

 it is asserted that it was without adherent matrix, and without 

 the moisture which it would possess had it been imbedded in the 

 cave for ages. These assertions are disproved by the facts that 

 the tooth unfortunately split in pieces in process of drying, and 

 that the matrix of red earth, only partially removed when it was 

 repaired and gelatinised in the Ovens College Museum, is still 

 to be seen in the pulp cavity. 



In the exploration of the caves, in 1S76, the discoverer, Mr. 

 Mello, was director, while I undertook to name and classify the 

 remains, and we drew up a report published in the Quart. Geol. 

 Soc. Jouru., 1877, p. 475. Mr. Heath and myself acted as 

 superintendents of the work, under the direction of Mr. Mello. 



It was Mr. Heath's duty as superintendent to handover to the 

 director the notes on which the above assertions are based, as 

 well as any other notes relating to the work entrusted to him. 

 He did not do so. If he had any fault to find, it was his duty 

 to lay it before the committee, and in the interest of truth to 

 make his statement when the report was read at the meeting of 

 the Geological Society, at which he was present. He did neither 

 of these things. Nor when he had many opportunities of saying 

 what he liked at the meeting of the British Association at Shef- 

 field, after my paper before the Geological Section, and our 

 addresses at Cressw ell, did he say one word, although he was 

 present at both. The pamphlet in question was to us the first 

 intimation that he differed with us as to the facts. 



In conclusion it only remains for me to add that Mr. Heath 

 was not a member of the Exploration Committee, that he was 

 merely a subordinate to Mr. Mello, and that, on his own show- 

 ing, he kept back for nearly three years notes considered by him 

 to be valuable, which he was in honour bound to communicate 

 at once to the director for the information of the committee — 

 notes which were as much the property of the committee as the 

 fossil remains discovered in the caves at their expense. I am 

 instructed that the only notes which he gave to the director were 

 certain measurements of the inside of the Robin Hood Cave, 

 which it was found necessary to have done over again. 

 W. Boyd Dawk ins, 

 Secretary of the Cresswell Caves Exploration 

 Committee, 1876 



"The Society^ for the Encouragement of Literature 

 and Science'' 



The attention of the Council of the Geological Society has 

 been called to the prospectus of a "Society for the Encourage- 

 ment of Literature and Science," in which the letters "F.G.S." 

 are appended to the name of one of the vice-i residents and to 

 that of the "Secretary-in-Chief." I have been directed by the 

 Council to make it generally known that neither of these gentle- 

 men is a Fellow of the Geological Society, as would naturally 

 be inferred from their use of these letters, and I shall feel greatly 

 obliged by your insertion of this note in your columns. 



Geological Society, W. S. Dalias, 



Burlington House, November 27 A<sist. Sec. Geol. Soc. 



The attention of the Council of the Linnean Society of 

 London has been called to a paper or prospectus of a " Society 

 for the Encouragement of Literature and Science," whereof W. 

 Sarjeant-Rodway is stated to be " Secretary-in-Chief," and 

 wherein the names Lewis Biden, A. Ware, and Joseph Blackburn 

 Leslie each appear followed by the letters F.L.S., which letters 

 are those appointed to indicate "Fellow of the Linnean Society" 

 —a chartered society. Its attention has also been called to 

 another paper apparently put forth by a *' Conchological Society 

 of London," wherein the name W. Serjeant-Rodway appears 

 as "Secretary and Founder," with the addition of the letters 

 F.L.S. (Lond.). 



As no one of these four gentlemen is a Fellow of the Linnean 

 Society, the Councilof the same Society has requested me to 

 make the fact known, and I shall therefore be much obliged if 

 you will be so kind as to give insertion to this letter in Nature. 



Linnean Society, Burlington House, St. George MlVART 

 Piccadilly, W., November 27 Zool. Sec. Lin. Soc. 



Does Sargassum Vegetate in the Open Sea? 



If the "correspondent in Nature, vol. xxi. p. So, under the 

 above title, would again refer to my communication in vol. xx. 

 p. 578, which I much regret he finds so unsatisfactory, he will 



see that the several statements and quotations it contains are 

 exclusively based upon " personal " observations made by myself 

 and by the naturalists on board the Challenger during our cruise 

 in the North Atlantic in the year 1873. In replying to his 

 inquiries in vol. xx. p. 552, I was only anxious to supply him 

 with what I considered to be the latest and the most reliable 

 information available on the subject, and which hardly deserves 

 to be qualified as " old reports" and as " a mixture of the prevalent 

 opinion since Columbus and observed facts." 



The term Sargasso Sea has been extended by geographers, and 

 not incorrectly so, to all oceanic areas where large aggregations 

 of sea-weed are met with, and it does not necessarily imply the 

 presence of Sargassum, i.e., Sargassum bacciferum in these 

 regions, since the original Spanish word Sargazo (in Portuguese 

 Sargaeo) simply means "sea-weed." I am, therefore, not sur- 

 prised that the correspondent should not have found any gulf- 

 weed while crossing the Pacific Sargasso Sea. 



Nor can the obscurity in which so many details Connected 

 with the gulf-weed are still involved be fairly ascribed to want of 

 observation on the part of the few naturalists who have had the 

 opportunity of studying this interesting alga in situ, that is to 

 say, in the middle of the North Atlantic, but rather to the great 

 difficulty, if not impossibility, of ascertaining the life-history of 

 a specimen accidentally found floating on the surface of the 

 ocean. For this reason I fear that some time may elapse before 

 the numerous questions put by the correspondent in vol. xxi. 

 pp. 80-S1 can be satisfactorily answered. A botanist stationed 

 for several seasons at Bermudas, or on one of the Bahama 

 Islands, might probably succeed in throwing some light upon the 

 successive stages in the growth and decay of Sargassum bacci- 

 ferum. J. J. Wild 



The Paces of the Horse 



I venture to offer the following illustration of the effect 

 produced on the eye by a horse galloping. 



I take a pencil, O A, and oscillate it rapidly between the posi- 

 tions O a and O a'. The impression produced on my eye is nn 

 indistinct fan-shaped figure, aOa', bounded by two rather dis- 

 tinct images of the pencil in its extreme positions O a and O o'. 

 The indistinctness of the fan-shaped figure is caused by the rapid 

 change of position of the pencil, which is reduced to a minimum 

 at O a and O a', where the pencil sw ings up to, and returns back 

 from, its extreme positions, passing over the same ground twice 

 in successive instants of time, and thus seeming to pause in the 

 immediate neighbourhood of those positions. An artist repre- 

 senting this effect would draw the indistinct fan-shaped figure ; 

 and the two rather distinct images of the pencil at O a and Oa'. 



The relative motion of the legs of a horse galloping may be 

 looked upon as that of rapidly oscillating pendulums with this very 

 important addition ; that besides their pendulum like osc llations, 

 they go through rapid interna/ changes of form, owing to the 

 bending, or doubling up, of the legs at the knees, hocks, 1 ml 

 fetlocks, at every stride. The rapidity of these internal changes 

 is reduced to a minimum w hen the leg is in its extreme outstretched 

 position. Again, it is in this same position that the rapidity of 

 change of position owing to the pendulum-like oscillation is also 

 at a minimum. The two minimums are, as it were, coincident, 

 and, as a consequence, every leg as it reaches its outstretched 

 position, eems for an instant to pause, leaving a rather distinct 

 im| ression on the eye. The other legs on successively reaching 

 their respective outstretched positions produce corresponding 

 impressions on the eye. It is a fact that the legs do not reach the: e 

 positions simultaneously ; they reach them successively, but the 

 image produced by one leg in its outstretched position has not 

 time to be obliterated before the images of the other legs are 

 produced in their corresponding outstretched positions. There- 

 fore they appear to us to be all simultaneously in those out- 



