io6 



NA TURE 



{Dec. 7, 1871 



New Zealand, May 5, 1869, and also in the "Annals and 

 Mag. Nat. Hist." October 1870. 



The skeleton of this animal has been lately placed 

 among the fine series of Cetaceans in the Musemn of the 

 Royal College of Surgeons, thanks to the extremely 

 liberal desire of Dr. H last that it should be made as 

 available as possible for scientific examination, com- 

 parison, and description, and to the generosity of Mr. 

 Erasmus Wilson, F.R.S , a member of the Council of 

 the College, in providing the means of adding it to the 

 collection without expense to the Institution. A detailed 

 and fully illustrated description of this skeleton formed 

 part of the communication to the Zoological Society 

 alluded to above, and will appear shortly in the " Trans- 

 actions.'' -All the characters of the skeleton agree generally 

 with those of the other Ziphioids, but it appears in some 

 respects to be a less specialised form, approaching some- 

 what nearer to the true dolphins, while Hypcroodan is at 

 the other extremity of the series, being modified in the 

 direction of the sperm whales. It has two teeth on each 

 side of the lower jaw, situated near the front end or 

 symphysis, which show nearly the same characteristic 

 and peculiar structure as that described by Mr. Ray 

 Lankester in the teeth of Mesoplodon Sowerhyi. The 

 skull is far more symmetrical than in any other member 

 of the group, and wants the great maxillary crests of 

 Hvpcroodoii, and the dense ossification of the rostrum 

 found in so many of the others. The cervical region is 

 comparatively long, with the majority of its verlebrse free, 

 the dorsals and ribs are ten in number, the lumber and 

 caudals thirty-one, making forty-eight in all- Viewing 

 the skeleton as a whole, the most striking feature is the 

 small size of the head compared with the great length of 

 the vertebral column, and the massiveness of the indi- 

 vidual bones, especially of the lumbar and anterior cau- 

 dal vertebric. It presents in this respect a remarkable 

 contrast to the sperm whale, which hangs near it in the 

 museum, though agreeing generally wilh the other 

 Ziphioids. As before mentioned, it is thirty feet in length, 

 and, as Dr. Haast was able to obsci-ve, it agrees with its 

 congeners in the nature of its food, for its stomach was 

 found to contain about half a bushel of the horny beaks 

 of cephalopods. The colour of the whole animal when 

 fresh was of a deep velvety black, with the exception of 

 the lower portion of the belly, which was greyish. 



Extinct Ziphioids. — To the circumstance of the extreme 

 density of the rostral portion of the skull of certain 

 Ziphioids, owing to the firm ossification of the mesethmoid 

 cartilage and its coalescence with the surrounding bones 

 (the maxilla, prcmaxilla, and vomer) our knowledge of 

 many of the ancient members of this group of whales is 

 due. When all other portions of the skeleton have yielded 

 to the destructive influence of time, these rostra, generally 

 in the form of elongated and somewhat flattened cylin- 

 ders, worn and eroded by the action of water, gravel, and 

 sand, occasionally come to light to attest the presence of 

 a former world of oceanic life. A few teeth also have 

 been found which would appear to be referable to these 

 same animals. Tlie localities in which these occur in 

 England are the Red Crag deposits of Suffolk. They are still 

 more abundant, and in a much more perfect condition in 

 the beds of corresponding age in the neighbourhood of 

 Antwerp, which have fortunately been laid bare Ijy the 

 excavations made in the defensive works of that city. A 

 magnificent series of these fossils containing many new- 

 forms has recently been added to the Brussels Museum, 

 but until M. le Vicomte Du Bus, the accomplished late 

 Director of the Museum, has completed the great task 

 he has undertaken of determining and describing them, 

 Uiey are as little available for zoological science as if thev 

 Jftlll lay 



III the bottom of the deep 

 W lieii- falliom line could never touch the Kroiinil. 



W. H. Flower 



CONTINUITY OF THE FLUID AND GASEOUS 

 ST A TES OF MA TTER * 



"VVTHEX we find a substance capable of existing in two fluid 

 ' ' states different in density and other properties, while the 

 temperature and pressure are the same in both ; and when we 

 find also that an introduction or abstraction of heat without 

 cliange of temperature or of pressure will effect the change from 

 the one state to the other ; and also find that the change either 

 way is perfectly reversible, we speak of the one state as being an 

 ordinary gaseous and the other as being an ordinary liquid sta^e 

 of tlie same matter ; and the ordinary transition from the one to 

 the other we would designate by the terms boiling, or con- 

 densing ; or occasionally by other terms nearly equivalent, such 

 as evaporation, gasification, liquefaction from the gaseous state, 

 &c. Cases of gasification from liquids, or of condensation from 

 gases, when any chemical alteration accompanies the abrupt 

 change of density, are not among the subjects proposed to be 

 brouglit under consideration in the present papei'. In such cases 

 I presume tliere would be no perfect reversibihty in the process ; 

 and if so, this would of itself be a criterion sufficing to separate 

 them from the proper cases of boiling or condensing at present 

 intended to be considered. If now the fluid substance, in the 

 rarer of the two states — that is, in what is commonly called the 

 gaseous state — be still further rarefied, by increase of temperature 

 or diminution of pressure, or be changed considerably in other 

 ways by alterations of temperature and pressure jointly, without 

 its receiving any abrupt collapse in volume, it will still, inordinary 

 language and ordinary mode of thought, be regarded as being in 

 a gaseous state. Remarks of quite a corresponding kind may be 

 made in describing various conditions of the fluid (as to tempe- 

 rature, pressure, and volume), which would in ordinary language 

 be regarded as belonging to the liquid state. 



Dr. Andrews (Phil. Trans. 1S69) has shown that the ordinary 

 gaseous and ordinary liquid states are only widely separated formj 

 of the same condition of matter, and may be made to pass into 

 one another by a course of continuous physical changes presenting 

 nowhere any interruption or breach of continuity. If we denote 

 geometrically all possible points of pressure and temperature 

 jointly by points spread continuously in a plane surface, each 

 point in the plane being referred to two axes of rectangular co- 

 ordinates, so that one of its ordinates shall represent the tempe- 

 rature, and the other the pressure denoted by that point ; and if 

 we mark all the successive lioiling- or condensing-points of tem- 

 perature and pressure as a continuous line on this plane ; this 

 line, which may be called the boiling line, will be a separating 

 boundary between the regions of the plane corresponding to the 

 ordinary liquid state and those corresponding to the ordinary 

 gaseous state. But, by consideration of Dr. Andrews's expe- 

 rimental results, we may see that this separating boundary 

 comes to an end at a point of pressure and temperature, which, 

 in conformity with his language, may be called the critical point 

 of pressure and temperature jointly ; and we may see that, from 

 any ordinary liquid state to any ordinary gaseous state, the tran- 

 sition may be effected gradually by an infinite variety of courses 

 passing round outside the extreme end of the boihng line. 



Now it will bo my chief object in the present paper to stale 

 and support a vie*' which has occurred to me, according to which 

 it appears probable that, although there be a practical breach of 

 continuity in crossing the line of boiling-points from liquid togas 

 or from gas to liquid, there may exist in the nature of things a 

 theoretical continuity across this breach, having some real and 

 true significance. This theoretical continuity, from the ordi- 

 nary liquid state to the ordinary gaseous state, must be sup- 

 posed to be such as to have its various courses passing through 

 conditions of pressure, temperature, and volume in unstable 

 equilibrium for any fluid matter theoretically conceived as homo- 

 geneously distributeil while passing through the intermediate 

 conditions. Such courses of transition, passing through u'-siable 

 conditions, must be regarded as being impossible to be brought 

 about throughout entire masses of fluids dealt with in any jiliy- 

 sical operations. Whether in an extremely thin lamini of gradual 

 transition from a liquid to its own gas, in which it iitobe noticed 

 the substance would not be homogeneou-ly distributed, contli- 

 tions may exist in a stable state, having some kind of correspond- 

 ence with the unstable conditions here tli'roretically conceived, 



" Considerations on the abrupt change at boiling or condensing in re- 

 ference to the Continuity of the Fluid State of Matter, '* by Professor James 

 Thomson, LL.D., Queen's College, Belfast, read before the Royal Society, 

 Nov. 16, 1871. 



