460 



NATURE 



{March 14, 18B9 



The demand for works like the present, we are glad to 

 think, is likely to increase. It is in the examination of 

 the embryology and in the dissection of insects in their 

 various stages of development that the labours of entomo- 

 logists will be largely engaged when the discovery and 

 description of new species of insects begin to grow slack. 



It is when we consider the vastness of the subject of 

 entomology, and the practically inexhaustible field of in- 

 vestigation lying before us, that we feel grateful for such 

 works as Dr. Packard's, which bring before us in a concise 

 form recent methods employed in the treatment of sub- 

 jects always difficult to manipulate and to render fit for 

 microscopic examination. O. S. 



The First Ascent of the Kasai: being some Records of 

 Set vice under the Lone Star. By C. S. L. Bateman. 

 (London : George Philip and Son, 1889.) 



When Lieutenant Wissmann made his memorable de- 

 scent of the River Kasai, he was accompanied by a 

 number of natives whose good-will he had secured by 

 wise and kindly treatment. At Ldopoldville, whence 

 Lieutenant Wissmann returned to Europe, it was decided 

 that Dr. Wolf should take the various members of this 

 escort back to their homes, and that the Expedition under 

 his command should be sent on to establish a station at 

 the confluence of the Lulua with the Luebo. This Expedi- 

 tion was joined by Mr. Bateman as second in command ; 

 and in the present volume he records his experiences in 

 the ascent of the Kasai, and during the time when he was 

 engaged in directing the making of the Luebo station. 

 Mr. Bateman is sometimes tempted to indulge rather too 

 much in fine writing, but, notwithstanding this drawback, 

 his book is one of considerable interest. He gives a good 

 general idea of the manner in which he was impressed 

 by the scenery through which he passed or in the midst 

 of which he lived ; and he is at great pains to describe, as 

 accurately as possible, the various native tribes with whom 

 he came in contact. Above all, the book is valuable for 

 the light it throws on the influence that is being exerted 

 by the Congo State. Mr. Bateman worked as one of its 

 officials at the Luebo station, and no one who reads the 

 record of what he accomplished can doubt that acting 

 through such agents the new State is preparing the way 

 for the growth of legitimate commerce, and for the 

 development of wholesome relations generally between 

 Europeans and the natives. The volume contains many 

 illustrations, produced from the author's original sketches 

 in pencil, water-colour, pen and ink, or sepia. 



Tabular List of all the Australian Birds. By E. P. 

 Ramsay. Pp. 1-38, with Map. (Sydney: Pubhshed 

 by the Author, i8»8.) 



The present list by Dr. E. P. Ramsay shows that a 

 considerable increase in our knowledge of Australian 

 ornithology has taken place since the year 1878, when 

 the author last issued a list of the birds of Australia. 

 The method adopted in this most useful publication is of 

 the simplest and most effective nature, fourteen natural 

 districts being recognized by Dr. Ramsay, and the dis- 

 tribution of each species being shown by an indication of 

 a number corresponding to the number of the district in 

 the table, so that the known range of every Australian 

 species is seen at a glance. References are given t^o all 

 the newly-described species, and on the opposite page to 

 each table Dr. Ramsay gives critical notes of great im- 

 portance to the student. A map is also given which 

 indicates the natural areas of the different provinces of 

 Australia, and enumerates most of the places where well- 

 known collections have been made. A list of the 39 

 species known from Lord Howe Island and Norfolk 

 Island is also appended, and a new species of owl from 

 the former is described as Ninox albaria. 



R. B. S. 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature, 

 No notice is taken of anonymous communications. ] 



The Meteoric Theory of Nebulae, &c. 



In his interesting letter (p. 436), Mr. Preston draws attention 

 to a point which was not referred to in my paper. 



It has generally been supposed that the incandescence of the 

 trail of a falling star was an evidence of the volatilization of the 

 solid materials of a meteorite, and in the lower regions of the 

 atmosphere this must certainly be true to a greater or less degree. 

 But, in a paper read before the French Academy on February 18 

 (see abstract in Nature, February 28, p. 432), M. E. Minary 

 argues that the incandescence of meteorites cannot be explained 

 by the transformation of motion into heat ; and, after the read- 

 ing of the paper, M. Cornu remarked that the luminosity of the 

 trail of a meteorite might be an electrical phenomenon, without 

 any considerable rise of temperature. I quote this in order to 

 show that we should be cautious in accepting Mr. Preston's 

 conclusion as to the rapid retardation and volatilization of 

 meteorites when moving through a highly rarefied gas. 



It may be admitted that, when a swarm of meteorites is closely 

 packed, it will soon assume the form of gas throughout, but I 

 cannot believe that gaseous friction affords a valid objection to 

 the meteoric theory, when the meteorites are in loose order. 

 The solidification of volatilized metals would, I suppose, take 

 place in a few minutes or seconds, and the mean interval be- 

 tween collisions was shown, in my paper, to be conveniently 

 measured in hours or days. It would not be unreasonable to 

 suppose that the so-called permanent gases also solidify, when 

 cooled to the low temperature which must obtain. But, apart 

 from this possible solidification, Mr. Lockyer suggests that the 

 permanent gases would be quickly occluded in the solids 

 volatilized at the same instsnt. 



The fusion of meteorites, so as to compensate fractures, forms, 

 as I have myself said, perhaps 'he most serious difficulty in the 

 theory. It cannot be supposed that fusions take place except 

 under favourable circumstances ; but, if a swarm of meteorites 

 does not degrade into dust, these favourable circumstances must 

 occur often enough to counterbalance fractures. 



Mr. Preston does not seem to be correct in respect to 

 Clausius's theory of the constant ratio of internal to translatory 

 energy in a gas. Clausius assumes, and does not prove that, in 

 the average of a number of collisions, the molecule will absorb 

 an amount of energy proportional to the mean violence of the 

 blows with which it has been struck. Clausius's law must be at 

 least approximately true within considerable variations of tem- 

 perature, but it is certainly not a rigorous law of mechanical 

 systems. 



The case of meteorites in collision is totally different ; they 

 are incapable of taking up more than an infinitesimal amount of 

 vibratory energy. The energy which, in the molecules of a gas, 

 is absorbed, in the case of meteorites goes in volatilizing solids. 

 There seems to be no reason why the particular ratio which 

 Clausius determines from the numerical value of the ratio of the 

 two specific heats (7) in a gas, should hold good in a swarm of 

 meteorites. We have no idea of the ratio of the two quasi- 

 specific heats in a swarm of meteorites, and therefore we are 



not entitled to use the equation )3 = | , and to put 7 = I -4, 



deducing j8 = f ^ In other words, I do not see room for making 

 any deduction as to the ratio between the kinetic energy of a 

 swarm of meteorites and the thermal energy existing in the 

 volatilized gases. 



I fail to see any parallelism between Clausius's law and the 

 conclusion drawn as to the lost potential energy in the formation 

 of a swarm of meteorites. The loss of energy is an outcome of 

 the law of gravitation, as applicable to the formation of a gaseous 

 star, and is deducible without any reference to the kinetic theory 

 of gases, or to its analogue for meteorites. 



G. H. Darwin. 



'■ Maxwell, "Theory of-Heat " (1875), p. 317. Mr. Pres'.on's statement 

 of the law is itiaccilrate. 



