April 8, 1880] 



NATURE 



537 



Elephas planifrons. In that species the premolars do verti- 

 cally displace the milk-molars, as is shown in the "Fauna 

 Antiqua Sivalensis." 



p_ jgg_ — Dinothcrium is not mentioned as occurring in India, 

 and D. gigauttum is said to be the only species. Two species 

 v ere named by Falconer in India ! 



P. 395. — We read : " The earliest remains of Melidte are 

 from the upper miocene deposits of the Siwalik Hills in Indin, 

 in which we meet with the living genus Mellivora (comprising 

 the Honey-Badgers), and the allied but extinct Ursitaxus." 

 Ursitaxus is not an extinct genus, but the generic synonym given 

 by Hodgson for Mellivora indica I There is only one species of 

 Metida from the Siwaliks, Mellivora ( Ursitaxus) sivaltnsis. 



p. -596. — Ietitherium is mentioned as occurring only in Attica, 

 no notice being taken of the Indian species de.-cribed in our 

 Records for February, 1S77. 



P. 402. — Pscuditltirus is only mentioned from Europe and 

 America, the Siwalik species described in our Records for May, 

 1877, being ignored. 



Other instances of omission occur in the book, which might 

 be noticed here, but sufficient have been quoted to show that as 

 regards Indian vertebrate paleontology, even up to the beginning 

 of 1878, the work is not trustworthy. It is to be presumed that 

 a writer would not willingly disfigure his own work, yet what 

 can be said of a compiler who, in writing on Indian paleontology, 

 omits to refer to the publications of the Geological Survey of 

 that country. Richard Lydekker 



Indian Museum, Calcutta, February 3 



The Mean Free Path of Molecules 



Mr. CrOOKES estimates that a bulb <^\ inches diameter, 

 attenuated i,ooo,ooo-fold, would contain a trillion of mole- 

 cules. 



Assuming in round numbers such a space to contain 100 cubic 

 inches, there would be io.oco billions per cubic inch. 



The molecules, considered as mathematical points, would have 

 a mean distance apart of less than 000C05 inches. 



The cube of 200,coo gives S,ooo billions instead ot 10,000; 

 therefore a linear inch would contain more than 200,000 in any 

 direction. 



How then can (he mean free path of actual molecules be 

 considered as from 2 to 6 inches? S. E. P. 



The Zoological Station, or Aquarium, at Naples 



When, la»t week, you referred to the account in the Daily 

 A\:os of the above-named institution, ycu omitted what you 

 probably did not know, which is, that, as you will see by the 

 accompanying copy of a letter from Dr. Anton Dohm to Dr. 

 W. B, Carpenter, it was I who devised all the aquarium portions 

 of the place, and that my ideas were carried out by the engineers, 

 Messrs. Leete, Edwards, and Norman. But I had nothing to do 

 with the laboratory part of the establishment. 



We are now so accustomed to aquaria, as being useful adjuncts 

 to biological studies, that it may surprise mm; persons to be 

 informed that in the earliest published official notice of the 

 Crystal Palace, Sydenham, a now very rare duodecimo of thirty- 

 five pages, dated September 22, 1852, it is stated on pages 22 and 

 23 that, owing to the difficulty, amounting to what seemed to be 

 impos ibility, of exhibiting living marine animals inland, in sea- 

 water, they, the fish, Crustacea, mollusca, zoophytes, &c, would 

 be shown dead, but, " on a plan not hitherto tried, that of making 

 them appear to be swimming in very large glass vessels containing 

 a sufficient quantity of some preservative fluid having the appear- 

 ance of water." 



Something of this kind was attempted by Dr. Bowerbank, but 

 it was not till the year 1870, after applying for fifteen years, that 

 1, assisted by the same engineers, was permitted to arrange the 

 aquarium now existing there, and which possesses the same sea- 

 water, never since renewed, nor has it been changed in marine 

 aquaria, which I set up in Paris in i860 and Hamburg in 1862. 



It is a pity that no one in Britain seems inclined to work our 

 British aquatic animals, marine and fresh-water, as Dohm 

 exhibits and studies those of the Mediterranean and the rivers 

 adjoining it ; and British creatures of the same range of organisa- 

 tion, viz., sponges to fishes, are quite as interesting and almost as 

 brilliant as those of the South of Europe. 



We can, with modern appliances, possess these forms of life 

 in perfect health, even inland, especially as recent improvements 



in manufacturing artificial sea-water causes it to be quite as good 

 and as lasting as water from the sea. In Berlin and Hanover it 

 has been so used for years on a large scale. In a small way it 

 was employed long ago by Warington, Gosse, and by myself, 

 and now, in the February, 1SS0, number of the Midland Natu- 

 ralist, can be seen how wonderfully successful Mr. H. W. Jones 

 has been with it in a great aquarium, in conjunction with me, in 

 a place where water brought from the ocean would have co't 

 more than six times as much. W. A. Lloyd 



4, Zingari Terrace, Gipsy Road, Lower Norwood, April 6 



Ice Crystals and Filaments 



Something very like the " comb-like masses of ice " appears 

 upon the surfaces of plaster-models such as dentists make, after 

 they have been coaled with a preparation called Z/.y, 

 except that it is finer and -woolly. It seems to be caused by the 

 conti action of the models forcing out very fine jets of water or 

 watery vapour, which dis r olves the coating and spins it out until 

 dried and fixed in the shape we find it. The varnish is readily 

 soluble in water. S. T. BARRETT 



Port _Tervis, New York, U.S., March 20 



Ozone 



Will you please allow me to make a suggestion concerning 

 an additional element of observation at climatological stations ? 

 I refer to the observing of ozone. As the salubrity of a district 

 to a great extent depends on this powerful factor, w-ould it not be 

 well to include ozone in climatological observations, especially in 

 the case of hill and valley stations ? The tests would, I think, 

 at least enable some conclusions to be drawn as to the purity and 

 salubrity of the atmosphere at the different health resorts, and 

 in my opinion present means, even though imperfect, should on 

 no account be neglected until better are found. They might be 

 exposed on a hook in Stevenson's thermometer screen, as recom- 

 mended by Mr. Buchan ; but I find that this plan is only of 

 service during dry weather, and I think Clarke's ozone cage is 

 preferable. Clement L. Wragge 



Farley, near Oakamoor, Cheadle 



Meteors 

 On the night of April 4, between 10.5 and 10.25 p.m., I 

 observed the following four meteors, viz. : — 



1. Crossing the "Chair of Capiopceia," at an angle of 45 

 with the horizon, from the direction of Ursa Minor. Course 

 about 20°, time about 2 seconds, leaving a train. 



2. From 10 ea>t of Capclla to 10' below Kegulits, nearly 

 parallel with the horizon, passing below Castor and Pollux ami 

 above Procyon. Course about So°, time about 5 seconds, leaving 

 a train, and breaking up into several fragments before its final 

 disappearance, the fragments travelling one behind the other in 

 the same direction. I have never before seen a meteor of this 

 kind with so long a course. 



3. From 10° west of Castor and Pollux, to 5" west of them, 

 leaving a train. The trains of these three meteors were all of 

 the same bluish white colour. Their radiant points would 

 probably be somew here betw een Ursa Minor and Cas. 



4. In exactly the contrary direction, just above Castor and 

 Poll it v. Course about 5", leaving no train, or a very faint one. 



Birstal Hill, Leice=Ur F. T. MOTT 



The meteor de cribed by your correspondent "B. W. S. 

 was also observed by me at Bristol traversing a long path of 59 

 from 247 + 42' to 200' =t o\ It was brighter than Jupiter, and 

 travelled very slowly, the estimated duration being 7 or 8 seconds. 

 The nucleus cast off a tail of sparks as it went along, and varied 

 very perceptibly in brightness. At mid-course it seemed near 

 extinction, but suddenly revived to its previous brilliancy, which 

 was then sustained until near the end point. 



A comparison of the meteor's track, as recorded at the two 

 places, shows it to have been directed from a radiant near ^ Cygni 

 (at 297° + 52°), and it is important to know whether any observa- 

 tions were made at additional places. The long duration of the 

 meteor and its very conspicuous apparition in the evening sky 

 must have brought it under the notice of a host of observers. 



Ashley Down, Bristol, April 5 W. F. Denning 



