July 13, 1905] 



NATURE 



263 



pearance of a grating could be produced in the field of 

 the microscope without there being anything on the stage. 

 The lines seen were achromatic interference bands pro- 

 duced with the help of two of Thorp's gratings of equal 

 pitch placed behind the objective. — Mr. Rousselet directed 

 attention to a living specimen of PltimateUa punctata 

 (Hancock) sent by Mr. Hood, of Dundee. The rare fresh- 

 water polyzoon has apparently not been recorded in 

 England since its discovery by Hancock in 1850. It differs 

 from other species of Plumatolla mainly in having a soft, 

 transparent ectocyst. — A communication by Mr. E. M. 

 Nelson on the tubercle bacillus was taken as read. — 

 Mr. A. E. Conrady gave a resume of his second paper 

 on theories of microscopic vision. In his former paper 

 he dealt with the formation of the image of a simple 

 plane grating, showing that it could be fully accounted 

 for on the basis of Abbe's theory. In the present paper 

 he considered more complicated structures, such as dot- 

 and cross-line patterns. 



Geological Society, June 21. — Dr. J. E. Marr, F.R.S., 

 president, in the chair. — The relations of the Eocene and 

 Cretaceous rocks in the Esna-.\swan reach of the Nile 

 Valley : H. J. L. Beadnell. .\t the meeting of the Inter- 

 national Geological Congress held in Paris in 1900, the 

 author brought forward evidence from the Baharia Oasis 

 and Abu Roash to show that there was a marked un- 

 conformity between these two systems in the northern 

 part of the country. The Jebel-Awaina succession shows 

 that in the southern part of the country, where the Upper 

 Cretaceous and the Lower Eocene occur in their fullest 

 development, there is no sharp line of demarcation between 

 the Cretaceous and the Tertiary, and no disturbances in 

 the stratigraphical succession. This is confirmed by the 

 succession in the Kharga Oasis, where there is no trace 

 of an unconformity. Dr. J. Ball's conclusions to the con- 

 trary were mainly based on the supposed irregular varia- 

 tion of the Esna Shales; but, where this occurs, it is 

 mainly due to the fact that, with a slight increase of 

 carbonate of lime, these beds became almost indistinguish- 

 able from the overlying marls and marly limestones of 

 the Eocene. The author finds in Jebel Nur el Ghenneiem 

 some 180 feet of green clays between the Echinocorys- 

 Chalk and the Eocene marls and limestones, and a per- 

 fectly conformable succession throughout. Near Ain Amur 

 there is a considerable development of fossiliferous lime- 

 stones at the summit of the Cretaceous rocks, and many 

 of the fossils are hardly distinguishable from Eocene 

 species. The author is of opinion that the Farafra suc- 

 cession falls into line with that which obtains in the 

 southern part of the country, .^n important piece of 

 confirmatory evidence is furnished by the discovery of a 

 rich fauna in " ashen-grey clays " in the Esna-Aswan 

 reach of the Nile Valley by Dr. W. F. Hume, in the 

 clays above the Pecfen-Marls in the neighbourhood of 

 Esna. — \ contribution to the study of the Glacial (Dwyka) 

 Conglomerate in the Transvaal : E. T. Mellor. The survey 

 of a district lying east of Pretoria and extending from 

 near the diamond-fields to Middelburg has recently 

 afforded much additional information with regard to the 

 Glacial Conglomerate in this part of South Africa. The 

 district lies on the northern edge of the principal area 

 occupied by the Karroo system, and includes a number of 

 outliers, the area between which affords information as 

 to the source of the material of the Conglomerate and 

 the character of the land-surface on whicfi it was de- 

 posited. This surface is smoothed, grooved, and scratched 

 by ice-action. The Karroo system is here only 400 or 

 500 feet thick, and the Conglomerate usually about 50 

 feet ; but, where deposited in hollows, it may reach 200 

 feet or more in thickness. The fragments are usually from 

 I to 3 feet in diameter, but may attain as much as 8 or 

 10 feet; they are often facetted and sometimes show 

 striations. The majority of the boulders are of local 

 origin. True bedding-planes are rare in the conglomerate, 

 but there are included patches of sandstone, mudstone, or 

 shale, some of which show ripple- or eddy-markings. The 

 striae are remarkably constant in direction, and they and 

 the transport of boulders indicate an ice-movement from 

 the north-north-west to the south-south-east. In the 

 Prieska district Rogers and Schwarz found the movement 



to have been from north-north-east to south-south-west, 

 and the same direction is given by Schenck from near 

 the junction of the Orange and Vaal Rivers. During 1904 

 outliers of the Conglomerate were found farther north, 

 near the junction of the Elands and Olifants Rivers. — On 

 new Oolitic strata in Oxfordshire : E. \. Walford. — The 

 causes of variegation in Keuper Marl and in other calcare- 

 ous rocks : G. T. Moody. The author concludes that the 

 variegation of the Keuper Marls and of other calcareous 

 rocks has been brought about by the percolation of chaly- 

 beate water through the light-coloured mass, the more 

 porous parts of which have in consequence become stained 

 with ferric oxide, while the harder and more crystalline 

 parts, being non-porous, have remained unchanged. The 

 uniformity in distribution of ferric oxide in some red 

 rocks, such as the New Red Sandstone, suggests that the 

 iron contained in them has probably been derived from 

 chalybeate water in a similar manner. 



Challenger Society, June 2S. — Dr. R. N. Wolfenden 

 in the chair. — Dr. H. R. Mill exhibited the new chart 

 of the world, recommended by the International Geo- 

 graphical Congress, and published at the cost of the Prince 

 of Monaco. From 72° N. to 72° S. are sixteen sheets on 

 Mercator's projection ; each polar chart of four sheets is 

 on a circular projection. The submarine contours and 

 soundings are in metres, symbols indicating the bottom 

 deposits. The land is black ; the contours of the ocean 

 are coloured in deepening shades of blue. Meridians (from 

 Greenwich) and parallels are ruled for each degree. — Dr. 

 W. T. Caiman exhibited the two Decapoda brought from 

 the Antarctic region by the Discovery. Cranzon antarcticus 

 and Chorismus antarcticus, and explained their bearing on 

 " bipolarity." — The Secretary showed a chart repro- 

 duced in line-process from one of the society s blank 

 charts, in order to show the method of preparation. — On 

 behalf of Messrs. E. W. L. Holt and W. M. Tattersall, 

 Dr. Caiman read a preliminary note on the Antarctic 

 Schizopoda captured by the Discovery. The collection con- 

 tained several new species of Euphausiidse and Mysidse, 

 and the authors were able to show that Euphausia 

 superba (Dana), Sars, E. Murrayi, Sars, E. australis, 

 Hodgson, E. glacialis, Hodgson, and E. antarctica, Sars, 

 are all referable to a single species. — The Secretary read 

 a note on the probable time required by the larva of an 

 epibenthic animal to cross the Atlantic, and made some 

 remarks on the desirability of revising the nomenclature 

 of ocean currents on an international basis. 



Paris. 

 Academy of Scienres, July 3. — M. Troost in the chair. 

 — The theory of algebraic surfaces : Emile Picard. — The 

 propagation of waves along a liquid compressible column, 

 composed of strips of unequal velocities and filling an 

 elastic horizontal tube, without longitudinal tension : J. 

 Boussinesq. — On camphoacetic and 5-camphopropionic 

 acids : .'\. Haller. Methyl camphocarbonate heated with 

 sodium methylate and iodoacetic ester gives methyl carb- 

 oxymethylcaniphoacetate, which, with alcoholic potash, 

 furnishes camphoacetic acid. A corresponding compound 

 is obtained by substituting ethyl yS-iodopropionate for the 

 ethyl iodoacetate in the original reaction, and from which 

 ;8-camphopropionic acid is obtained. — On the existence in 

 the black elder of a compound furnishing hydrocyanic 

 acid : M. Guigrnard. The number of plants from which 

 hydrocyanic acid can be obtained is increasing every year, 

 and it has been suggested that it represents the first 

 recognisable product of the assimilation of nitrogen in 

 plants. In the elder, the fresh leaf furnishes the largest 

 proportion of the acid, averaging 001 per cent. — Synthesis 

 of the three tertiary dimethylcyclohexanols and of the 

 hydrocarbons connected with them : Paul Sabatier and 

 A. Mailhe. The cresols are converted into methylcyclo- 

 hexanones by means of the reduced nickel reaction, and 

 these are converted by methylmagnesium iodide into the 

 corresponding tertiary alcohols, good yields being obtained. 

 The preparation, physical properties, and reactions of the 

 ortho-, meta-, and para-tertiary alcohols are described. — 

 On the evolution of the tertiary mammals. K reply to 

 the observations of M. Boule : Charles Deperet. A con- 

 troversial note dealing more especially with the ancestry 

 of the horse and bear. — M. P. Curie was elected a member 



NO. 1863, VOL. 72] 



