June 14, 1894J 



NATURE 



167 



ing the absence of carboniferous beds in the Nile Valley, he 

 reminded the Society that deposits of this age had been dis- 

 covered by Dr. Schweinfurth in the Wady el-Arabah between 

 the Nile and the Gulf of Suez. Dr. Irving, remarking on the 

 silicification of wood, said he wished again to emphasise the 

 difference in the action of carbonic acid in petrological changes, 

 according as it exi'iK'd as a free acid or in combination with a 

 ' base, as in sodium carbonate. The extent of the "Natron" 

 deposits pointed to the supply of alkaline waters over large areas 

 in former times, holding the mineral in solution. The reaction 

 of such waters upon the potash-felspar of the sands, furnished 

 by the disintegration of the crystalline rocks, would not lead to 

 the deposition of free silica (as in the ordinary process of 

 kaolinisation), because, while the potassium was taken up as a 

 , carbonate and carried away, the silica was also removed in 

 I solution, through combination with the sodium, to form sodium 

 I silicate. This last-named salt in solution would be readily 

 I decomposed by the organic acids and the carbonic acid fur- 

 nished by decaying vegetable tissue, the silica being then 

 deposited as a colloid in silii, and thus retaining the structural 

 forms of the original tissue. The author briefly replied. — 

 Notes on the geology of South Africa, by Mr. D. Draper. The 

 district considered includes Natal, Zululand, Swaziland, the 

 south-east part of the Transvaal, and the eastern part of the 

 Orange Free .State and of Basutoland. Phy>ically it compre- 

 hends : — (l) The Drakensberg Range; divided into (a) moun- 

 tain portion ; (/') hill-covered plateau ; [c) Highveld plateau ; 

 {2) the terrace along its foot ; (3) the coast-belt. Their 

 main features and characteristics were described. The geolo- 

 gical formations are : — 



[ I. Volcanic Beds. 



.- 2. Cave Sandstone. 



Upper. . p^^^ g^j^_ 



f™° I I 4. Molteno Beds. 



'^'^"'- [ I 5. Beaufort Beds. 



Lower. -, 6. Ecca Beds. 



( 7. Dwyka (Ecca) Conglomerate. 

 ( [Bokkeveld Beds, wanting,] 



j 8. Gats Rand (Zuurberg) Quartzite. 

 9. Dolomitic Limestone. 

 10. Table-mountain Sandstone. 

 I II. Malmesbury Schists. 

 1 12. Gneiss and Granite. 



Palaeozoic. 



— On the occurrence of dolomite in South Africa, by the same 

 author. A peculiar calcareo-siliceous rock, near Lydenburg. 

 described by Messrs. Penning and Crutwell as " Chalcedolite," 

 and a similar rock mentioned by Mr. Penning as overlying the 

 " Blackreef Series " of the Megaliesberg formation, have been 

 recognised as a dolomite. Mr. C. Alford has described a 

 " calcareous quartzite " as passing into dolomite and ultimately 

 into chert, and known as the "Elephant-rock" in Transvaal, 

 sometimes cavernous with underground water-. From his own 

 experience Mr. Draper has recognised the " Elephant-rock " in 

 the Potschefstroom, Lichtenburg, Malmani, and Lydenburg 

 districts as a real dolomite, with interstratified siliceous bands, 

 weathering into a brown earth like manganese oxide and super- 

 ficial siliceous debris. It has its place between the Table-moun- 

 tain sandstone and the quartzite of the Gats Rand (= Zuurberg 

 quartzite of the Cape). It has auriferous veins in Malmani and 

 Lydenburg. Dr. Schrenck has noticed a similar dark-blue 

 dolomitic limestone in Great Namaqualand. The deep water- 

 holes in it in Malmani are comparable with those found by F. 

 Gallon in West Central Africa. The great caves in Mashona- 

 land may belong to it. The extensive tufaceous deposits in 

 Griqualand-West, the Transvaal, and Orange Free State 

 were probably derived from this extensive dolomite. Mr. 

 Rutley, Mr. Nicol Brown, and Prof. T. Rupert Jones 

 took part in the discussion that followed. — Contri- 

 butions to the geology of British East Africa, by Dr. J. W. 

 Gregory. The author described moraines, stria;, glacial lake- 

 basins, perched blocks, and roches moutoiniJeiheXovi \\\e\>xesenl 

 limits of the glaciers of Mount Kenya, which he maintained to 

 indicate the existence of a "calotte" or icecap extending at 

 least 5400 feet farther down the mountain than the termination 

 of the present glaciers, and possibly farther, for in the bell of 

 forest detailed observations could not be made. He agreed 

 that this more extensive glaciation was produced by a greater 

 elevation of Mount Kenya, and that any theory of universal 

 glaciation is unnecessary, and indeed opposed by many facts in 



African geology. He discussed the probable influence of this 

 former glaciation on the meteorological conditions of the sur- 

 rounding area and the distribution of its flora and fauna. 



Paris. 



Academy of Sciences, June 4. — M. Loewy in the chair. — 

 On the composition of apophyllite, by M. C. Friedel. No 

 positive evidence of the presence of fluorine in this mineral 

 could be obtained with specimens from Bou Serdoun (.■\lgeria). 

 Instead of an acid reaction, the water evolved possessed an 

 alkaline reaction in the cases of specimens from Bou Serdoun, 

 Andreasberg, Guanajuato (Mexico), (xreenland. Nova Scotia, 

 and Utij (.Sweden). There is no fluorine in the samples 

 examined ; that reported by previous observers is probably due 

 to the imperfect methods of analysis employed ; on the other 

 hand, they contain ammonia in quantity varying from O'OJ to 

 o'5 per cent., possibly replacing a part of the potassium. The 

 evidence available is insufficient to settle the formula expressing 

 the composition of apophyllite. — Report on a memoir by M. 

 Bazin on experiments on the contraction of liquid jets and the 

 distribution of velocities in their interior, by MM. Resal, 

 Maurice Levy, .Sarrau, and Boussinesq. — Transmission of 

 sounds, by M. Henri Gilbault. The amplitudes of vibration 

 being represented by^, and distances by x, it is shown that the 

 law .X)' = a constant is not verified in practice for small values of 

 X. — On the value of the theoretical ohm, byM. A. Leduc. The 

 author shows that a part of a correction, considered unimportant 

 by M. Wuilleumier, must be applied to the results obtained by 

 the latter according to M. Lippmann's method. These results 

 then give for the length of a column of mercury at o' C. and of 

 I sq. mm. section representing the theoretical ohm, the value 

 lo6'32 cm. in place of 106267 cm. The revised value is Id 

 close accord with the mean of the best determinations made by 

 other methods. — On the method of transformation of work into 

 electric energy, by M. Vaschy. — On alternating currents and 

 Wheatstone's bridge, by M. II. Abraham. A method is de- 

 scribed for obtaining the frequency of the alternations by bridge 

 measurements. — The skiaicofe-optomilrc, by M. H. Sureau. A 

 description of the use and parts of an instrument for the 

 examination of the eye by opticians. — New researches on the 

 chloroboraciles, by MM. G. Rousseau and H. Allaire. The 

 author describes the production and properties of compounds of 

 zinc, cadmium, nickel, cobalt, and manganese having the 

 general formula 6MO . SBoOj . MCI.,.— On the r.:/<f of the trans- 

 formations of iron and carbon in the hardening of steel, by M. 

 Georges Charpy. The following conclusions are drawn from 

 the experimental results given. Hardening produces, among 

 other modifications, a transformation of the iron (characterised 

 by the breaking strain) and a transformation of the carbon 

 (characterised by the variation of the results by the Eggertz 

 test). The transformation of the iron appears to have but a 

 feeble influence on the breaking strain, whereas the transforma- 

 tion of the carbon appears to be correlative with the augmenta- 

 tion of hardness. — On a hydrobromide of cupric bromide and on 

 a red bromide of copper and potassium, by M. Paul Sabatier. 

 The formula CuBr„. IIBr. 2H._,0 is attributed to the substance 

 obtained in black chatoyant crystals by cooling a concentrated 

 solution of cupric bromide into which hydrogen bromide has 

 been passed. The double compound with potassium is 

 CuBr„ . KBr. It forms fine, deliquescent, rhombic plates, which 

 are very opaque and apparently black, but are seen to be red in thin 

 sections. — On the analytical separation of chlorine and bromine, 

 by M. R. Engel. The bromine is separated by oxidation with 

 ammonium persulphate, and distilled off into a sulphurous acid 

 solution, from which it is precipitated as silver bromide. Under 

 the conditions given, the chlorine is not affected. — On the 

 detection of hydrobromic acid, by MM. .\. Villiers and M. 

 Fayolle. — New derivatives of cyanacetic and cyanosuccinic 

 esters, by M. L. Barthe. — Combinations of pyridine with the 

 permanganates, by M. T. Klobb. A series of compounds parallel 

 with the ammonia derivatives previously described and of the 

 general formula MMnO^ . 2C,,Il5N or MMnjOg . 4C,H5N are 

 given. — ^On the emetics, by M. Paul Adam. The conclusion 

 is drawn that substances of the emetic type should be considered 

 as ether salts and not double salts. — On mcnoethylphosphoric 

 acid, by M. J. Cavalier. This acid exhibits, thermally, two 

 clearly distinct functions and gives two series of definite salts, 

 corresponding with the formuh-e POjElMH and POjEtM;. — 

 Action of trioxymethylene on alcohols in presence of ferric 

 chloride, and on the new methylene derivatives which result, 



NO. 1285. VOL. 50] 



