Feb. 4, 1886] 



ATA TURE 



331 



and Mathematical Chemistry." The main problem to which 

 the work addressed itself respected the nature and properties of 

 the imponderable matter, ether, but its arguments were, in the 

 main, drawn from fancy more than from experience. The work 

 was divided into three parts. The first part, the Constitution 

 of Bodies, formulated the theory that the ponderable atoms 

 were not qualitatively, but only quantitatively, distinguished 

 from one another ; that the elastic effect of matter on ether, as 

 on ponderable substances, diminished with the distance ; and 

 that the density of the ether ranged round ponderable matter 

 did not diminish in proportion to the distance from the mass of 

 atoms, but increased in proportion to the distance. As essential 

 to the constitution of the bodies was further advanced the 

 pressure of ether on the particles of ether ranged round the 

 ponderable atoms. The second part, the Principles of Chemis- 

 try, proceeded from the hypothesis that a material particle was 

 capable of attracting only one, or quite few, particles of ether, 

 noting in such a manner, namely, that a fraction of the attractive 

 force, now of the particle of ether, now of the mass particle, 

 was kept in abeyance {conditions which, for reasons otherwise 

 altogether unexplained, were termed " electro-neg.ative " and 

 "electro-positive" respectively), and made use of an accidental 

 property of the curve of the density of elements contained in 

 L. Meyer's " Modern Theory of Chemistry," namely, that in 

 the case of the maxima and minima of this curve, elements 

 related electro-negatively to the neighbouring elements in the 

 curve always passed over to such in which the reverse condition 

 obtained, in order, by calculations described by the author him- 

 self as highly uncertain, to determine the molecular magnitude 

 of some elements and the number of particles of ether attracted 

 by their atoms. The third part, the Doctrine of Heat, pro- 

 pounded heat as elastic concussions ; in elaborate calculations 

 brought forward for some examples of numbers the argument 

 that the occurrence of the stationary state was explainable under 

 this assumption likewise ; and contended against the Mariotte- 

 Gay-Lussacand Avogadro laws, which were incapable of rightly 

 explaining the facts, seeing that these laws and their deduction 

 took no account wdiatever of the imponderable ether and the 

 pressure of ether. 



THE HISTOR V OF FOSS/L CROCODILES 1 



TNthis communication the author endeavoured to summarise 

 the main facts already known regarding the palfeontological 

 history of the Crocodilia, with full references to the principal 

 literature of the subject. After some preliminary remarks upon 

 the structure and distribution of the living members of the order, 

 the leading types of each geological period were successively 

 considered ; and the ijaper concluded by discussing the bearing 

 of these facts upon the evolution of the Crocodilia, as deter- 

 mined by Prof. Huxley in 1875. The earliest crocodilians 

 hitherto discovered are Belodjii, Stagonolepis^ and Parasuchus, 

 from the Upper Trias — the first-named being met with on 

 the Continent, in India, and in North America ; the second, 

 solely known from the yellow sandstones of Elgin ; and the 

 third, only recorded as yet from India. The Rhjetic Beds and 

 Lower and Middle Lias do not appear to have yielded any 

 remains of this order, but numerous examples have been found 

 in the Upper Lias, and some in a remarkable state of preserva- 

 tion. At present, however, the precise systematic relationships 

 of the Liassic forms have not been veiy satisfactorily deter- 

 mined, and those from British deposits are especially in 

 need of further study : there are probably two generic types, 

 Mystriosauriis and Pelagosauriis, and, if the latest researches 

 are to be followed, it would seem that only two species 

 of each are definitely known. In England, according to 

 M. Deslongchamps, two distinct forms, Myslriosaurus chap- 

 viani and Peiagosnurus brongniartl. have been continually 

 described under the name of 7 eleosaurus chapntuni. With the 

 Lower Oolites, Tcleosau'iis proper makes its appearance, and 

 ranges at least as far upwards as the Kimmeridge Clay, from 

 which Mr. J. W. Hulke has described a characteristic snout 

 (7*. megarhinus). Sleneo5auj-u% is also a Lower Oolite form, 

 ranging to the Oxford Clay ; its British representatives are some- 

 what imperfectly known, though very complete descriptions have 

 been published of well-preserved cranial fossils from French 

 deposits. Mdriorhynchiis is another genus, from the Middle 



' Abstract of a Paper read ! 

 December 4, 1885, by Mr. l 

 Museum (Natural History). 



of the British 



and Upper Oolites, very fully elucidated by M. Deslongchamps 

 in France, but scarcely determined hitherto in English strata. 

 Two forms described by Prof. Phillips under the names of 

 Steneosaiiriis palpebrosiis (Kimmeridgian), and Steiivasaurus gra- 

 cilis (Porflandian) are truly referable to iVetriorhynchus, and 

 fragments agreeing specifically with some of the French Metrio- 

 rhynchs are also recorded. The Upper Oolites also yield the 

 remains of Crocodilia with comparatively short and stout skulls, 

 and very complete specimens have been discovered in the 

 Kimmeridge Clay both of England and the Continent. They 

 belong to the genera Dakosmiriis and Machimosaurus, the former 

 having also been described by Sir Richard Owen under the 

 name of Plesiosiichus. Teleosaurians occur rarely in the Wealden 

 and Purbeck Beds— though one or two well-preserved crania of 

 Macrorhynchus are known in Germany — and they finally dis- 

 appear in the Upper Cretaceous series, where they are repre- 

 sented by the scanty remains of Hyposaunis and Enaliosuchns. 

 Broad-faced crocodilians, adapted for a mote terrestrial mode of 

 life than the Teleosaurs, occur somewhat abundantly in the 

 Wealden and Purbeck Beds, and are represented by Goniopholis, 

 Nannosuc/iuSj Oweniasuchus^ TheriositchnSj and a remarkably 

 interesting genus — Bernissarlia — recently described by M. Dollo 

 from the now classical deposit of Bernissart in Belgium. The 

 latter, though decidedly Mesosuchian, approaches the living 

 crocodiles and alligators much more closely than any of its con- 

 geners, both in the characters of its dermal armour and in certain 

 parts of the skull. The earliest evidence of procojlian crocodiles 

 hitherto made known is from the Cambridge Greensand and the 

 nearly equivalent Gosau Beds of Vienna ; Prof. H. G. Seeley 

 has described a few vertebriK, teeth, and fragments of limb- 

 bones, and regards these as referable to at least three specific 

 types. The Upper Cretaceous beds of France and the United 

 States have yielded still more satisfactory remains — including 

 skulls — showing that the Eusuchian sub-order dates back beyond 

 Eocene times ; and some of these fossils appear almost indistin- 

 guishable from the living genus Gavialis. The early Tertiary 

 deposits, both of England and the Continent, are remarkable as 

 affording traces of gavials, crocodiles, and alligators (or alliga- 

 toroid genera) associated together, while the three families share 

 no common area of the earth's surface at the present time ; the 

 Eocene types, moreover, appear to be rather less differentiated 

 than is the case in the existing fauna. In conclusion, it may be 

 said that the abundant acquisitions of fossil Crocodilia during 

 the last ten years have luUy confirmed the views of Prof. 

 Huxley, laid before the Geological Society in 1875 ; and the 

 Wealden and Purbeck discoveries, particularly, have brought to 

 light facts which were then little more than probable surmises 

 based upon very fragmentary materials. 



PROFESSOR SYLVESTER'S LECTURE "ON 

 THE METHOD OF RECIPROCANTS AS CON- 

 TAINING AN EXHAUSTIVE THEORY OF 

 THE SINGULARITIES OF CURVES" 



pROFESSOR SYLVESTER sends us the following cor- 

 rections and additions to his lecture recently given in 

 Nature (January 7, p. 222) : — 



Eriaia 



P. 223, 1st column, line 27, for "requirements" read "ac- 

 quirements." 



P. 224, 1st column, line 37, for geometrical adjustment read 

 numerical adjustment. 



P. 225, in the footnote, for l_ read ^ 



P. 226, 2nd column, line 9, p. 227, ist column, lines 14, 20, 

 22, 31, 34, 44, and 2nd column, line 16 from bottom, in all thees 

 places for t read /, and in the last for t - t' read t - t'. 

 P. 226, 2nd column, line 5, 



dy dy dy 

 dx"-' di^' lil*' ' ' ' 



for 



read '^'^ "'^■^ ''''-'' 



"^'^ 1^'' d^' dl^' ■ ■ ■ 



P. 226, 2nd column, line 20, for "operation " read "operator." 

 P. 228, Ist column, line I, for t read /. 



P. 229, in the ist line of the footnote in the Ist column, for 

 "generating fraction" read "fractional generating function." 



