Fel>. 24, 1887] 



NA TURE 



407 



wilh precipitous walls, the fuimalion of a new lake between this 

 crater and Tarawera, and the formation of a number of small 

 craters about Okaro. The materials ejected were composed 

 of augite-andesite, and rhyolites, both compact and vesicular. 

 The n>ineral structure and distribution over the surround- 

 ing country of various forms of pumice, scoria, and ash were 

 described, and it was shown that there was a difference in 

 the substances ejected from the mountain craters of Tara- 

 wera and those from the craters in the plain at Rotomahani 

 and Okaro, the former comprising pumice and scoria, which 

 were not thrown out from the latter, and but little steam issuing 

 from the higher craters when compared with the enormous 

 volumes emitted from the lower vents. The eruption 

 was ascribed to the reheating of old lava-streams saturated 

 with water. This reheating was apparently not due to crushing — 

 for, had it been so, the )>receding earthquakes would have been 

 more violent — but probably to molten rock coming up from 

 below and heating the rocks near the surface. The eruptions 

 from Rotomahana and Okaro were purely hydrothermal. 



Chemical Society, February 3. — Dr. Hugo Miiller, F.R.S., 

 President, in the chair. — The following papers were read : — The 

 absorption of gases by carbon, by Charles J- Baker. — An ex- 

 planation of the laws which govern substitution in the case of 

 benzenoid compounds, by Henry E. Armstrong. Certain 

 mono-derivatives of benzene, especially those containing a 

 hydrocarbon radicle, one of the halogens, hydroxy! or amidogen, 

 yield a mixture of the para- and ortho-di-derivalives in propor- 

 tions which vary both according to the nature of the compound 

 dealt with and of the reagent, and the conditions under which 

 the change is eftected ; and if ])roduced at all, the meta-deriva- 

 tive is formed in but a small proportion. If, however, the 

 radicle present in the mono-derivative be — 



NO., COH, CO.,H, SO3H, 

 the metadi-derivative appears invariably to be the chief pro- 

 duct. Hitherto no explanation of this difference in the be- 

 haviour of the two series of mono-derivatives has even been 

 suggested. In seeking to arrive at an explanation it is necessary 

 to form a clear conception of the manner in which "substitu- 

 tion " is effected. The author is of opinion that in the first 

 instance an additive compound is formed; and he points out 

 that Kekule has long since insisted in the plainest terms on this 

 interpretation of those cases of change which are commonly 

 spjken of as "double decompositions." He is inclined to 

 believe that the tendency of negative to attract and combine 

 with negative elements — to which he has of late frequently 

 directed attention — is the effective |cause ; and that the additive 

 compound is formed from those mono-derivatives which obey 

 the " para-ortho law " by the fixation of the reacting _molecule 

 upon the carbon-atom which carries the radicle ; separation of 

 water or halogen hydride ensuing thereon, the radicle of the 

 reacting molecule assumes the place either of an ortho- or of a 

 para-hydrogen atom. It is easy to understand the formation of 

 the ortho-di-derivative, as the hj'drogen-atom displaced is asso- 

 ciated with a carbon-atom contiguous to that to whicli the 

 reacting molecule attaches itself. The formation of the para- 

 compound is attributed by the author to the tendency towards 

 symmetry, so frequently evidenced in cases of isomeric change 

 and in other ways by benzenoid compounds ; and not to the 

 existence of any direct connection between carbon-atoms rela- 

 tively in the para-position. The formation of meta-derivatives 

 is believed by the author to result from the addition of the 

 reacting molecule, not to the carbon-atom of the benzene-ring, 

 but to the radicle which in the mono-derivative is attached to 

 one of the cirbonatoms of the ring ; he is, however, of opinion 

 that in order to explain why the additive compound thus con- 

 stilu'ed yields a meta-di-derivative, it will be necessary to 

 obtain further information regarding the " dynamics " of such 

 changes. — Some derivatives of tetramethylene, by G. H. 

 Caiman and Dr. W. H. Perkin, Jun. — Derivatives of penta- 

 methylene, by Dr. \V. H. Perkin, Jun. — The decomposition of 

 potassium chlorate and perchlorate by heat, by Dr. Percy F. 

 Frankland and John Dingwall. — The action of chlorine on 

 methyl thiocyanate, by Dr. J. William James. 



Paris 



Academy of Sciences, February 14. — M. Gossehn, President, 



in the chair. — On waterspouts and M. Ch. Weyher's recent 



experiments, by M. Faye. While fully appreciating M. 



Weyher's novel and interesting essays, the author makes certain 



reservations, tespecially as regards the term troinbt: marine 

 (" waterspout ") applied by him to one of the results. This, he 

 submits, was not a true waterspout, but only a rotatory move- 

 ment of a volume of air without any defined limits, and with 

 aspiration towards the axis of the ventilator. But a true water- 

 spout is characterised by a cylindro-conical funnel sharply out- 

 lined, descending from the clouds to the ground or to the surface 

 of the sea, without exercising on it any perceptible aspiration. 

 — Note on MM. Paul and Prosper Henr)-'s photograph of the 

 nebula No. 1180 of Herschel's general catalogue, by M. 

 Mouche/.. During their photographic operations on Orion on 

 January 27, MM. Henry obtained an image of a nebula o.'' 3' to 

 4' diameter with stars of the 17th magnitude, invisible to ll'.e 

 observer with the equatorial of the East Tower. This nebiil.i, 

 which has also since been photographed by Roberts in England, 

 has now been identified with that discovered at the Cape by 

 Herschel, and by him indicated with the number 1 1 So in his 

 catalogue. — Reply to M. Houzeau's recent note on a method to 

 determine the constant of aberration, by M. Loewy. It is shown 

 that M. Houzeau's method of determining the constant from the 

 differences in right ascension or in declination as measured at 

 dffferent epochs, is liable to the most sarious errors. In virtue 

 of the diurnal movement, the two images are displaced in the field 

 of the telescope at different rates of velocity and in any direction, 

 their relative position changes from instant to instant, and under 

 the given conditions cannot be .accurately defined. — On a sand- 

 stone of organic origin discovered in the coal-fields of the Loire 

 basin, by MM. Favarcq and Grand'Eury. Notwithstanding their 

 chemical composition these remarkable deposits belong evidently 

 to fresh-water organisms, which cannot at present be further 

 identified. They abound especially in the Rive-de-Gier and 

 Saint-Etienne districts. — The inauguration of railw.iys in France : 

 its true date, by M. Leon Aucoc. It is pointed out that the 

 proposed celebration in 18S7 of the fiftieth anniversary of this 

 event re^ts on an historical error. The first line actually com- 

 pleted was that between Saint-Etienne and Andrezieux, 23 kilo- 

 metres long, opened on October I, 1S28 ; that is, nine years 

 before the assumed date 1837. — Remarks on the pala-ontological 

 researches made in the Lower Tertiary deposits in the neighbour- 

 hood of Rheims, by M. V. Lemoine. The author gives the 

 general results of his investigations carried on uninterruptedly 

 for the last fifteen years, and constituting the Rheims district one 

 of the points where the beginning of Tertiary life may be best 

 studied in Europe. The fossil vertebrates alone studied by him 

 now number 94, of which not more than 8 or 10 were previously 

 known. Amongst them are 40 mammals belonging to 23 differ- 

 ent genera, of which 8 only had hitherto been observed in later 

 Tertiary beds. — On the mode of formation of the striated Bilo- 

 bites, by M. Ed. Bureau. The author has obtained plaster casts 

 of most of these Bilobites, from a careful study of which he 

 concludes that they must represent imprints of animals on the 

 sands of shallow Silurian waters. — Combined action of bella- 

 donna and opium in a case of acute diabetes, by M. ViUemin. 

 After the usual remedies had failed, this treatment was lately tried 

 in an extreme case of diabetes at the Val-de-Grace Hospital, 

 with complete success. — Determination of the pDsition of the shaft 

 corresponding to a given position of the piston in a steam-engine, 

 by M. H. Leaute. Two remarkably simple graphic construc- 

 tions designed in 1869 by M. Marcel Deprez are described, by 

 means of which the position of the shaft for each position of the 

 piston may be determined with sufficient accuracy, when the 

 length-ratio of connecting-rod and shaft is greater than 3 — On 

 the application of photography to M. Loewy's new methods of 

 determining the elements of refraction and aberration, byM. Ch. 

 Trepied. An inquiry is here made into the conditions and 

 means by which M. Loewy's new and effective method of photo- 

 graphic registration might be utilised in determining the ele- 

 ments of astronomic refraction. — Observations of Barnard's and 

 Brooks's comets made with the 0-38 m. equatorial, Bordeaux 

 Observatory, by MM. G. Rayet and Courty.— On surfaces where 

 the difference of the chief radii of curvature is constant at each 

 point, by M. R. Lipschitz.^On a certain class of recurrent 

 sequences, byM. Maurice d'Ocagne. — On the specific heats of 

 liquids, by M. Marcellin Langlois. By the process here 

 described the author determines the specific heats of 

 water, sulphuret of carbon, chloroform, chloride of car- 

 bon, ether, alcohol, and acetone. — Researches on the 

 specific inducting power of liquids, by M. Negreano. The 

 author determines the dielectric constants of a series of homo- 

 logous and liquid carburets of hydrogen for the purpose of 



