28o 



NATURE 



\_yan, 23, 1879 



The Commission of the Municipal Council of Paris has 

 drawn up a report on the working of the electric light, which 

 has been printed, and was discussed on the 14th instant. A 

 certain number of important facts are stated. A JablochkofF 

 lamp may be said to give a quantity of light equal to eleven gas 

 lamps, consuming each 140 litres per hour. The quantity of 

 gas consumed to produce the same quantity of illumination 

 would be 1,540 litres per hour. The price paid by the city to the 

 gas company for 1, 000 litres being ofr. iSc, the expense would 

 be of o fr. 23 c. The expenses of each Jablochkoff lamp are 

 officially stated as follows, for 62 candles per hour of light, 

 77 horse-power : — Machinery, 3 fr. 20 c. ; coals for working 

 the several steam engines used, 6 fr. 64 c. ; oil for lubricating, 

 I fr. 23 c. ; pay of men for changing candles and superintending 

 illumination, 3 fr. 20 c. ; expenses of 62 candles at o fr. 50 c. 

 each, supposed to last during an hour, 31 fr. Total, 45 fr. 27 c, 

 or 73 c. for each candle. The Commission proposes to pay to the 

 JablochkofF company — which accepts o fr. 30 c. per candle during 

 one year — for 62 candles at the Avenue de I'Opera, 1 5 on the 

 Place de la Bastille, and 6 in a pavilion of the HaUes Centrales : 

 in all 83. The total number of burning hours is estimated at 

 2,073 for ^^^ of the street candles, and 4,000 for each of the 

 pavilion candles : altogether, 55,000. The expense paid to the 

 gas company for illuminating the same places is 21,041 fr. The 

 excess of expense for the city will be 34,044 fr. But this credit 

 is asked for in the interest of science. It is hoped that during 

 one year the Jablochkoff company will realise material improve- 

 ments, and it is supposed that other electric light companies 

 will tender some fresh propositions for comparison. In the 

 meantime, the Commission proposes to accept a tender made by 

 the gas company to improve the illumination of the Rue du 

 Quatre Septembre, Place du Chateau d'Eau, and a pavilion of 

 the Halles Centrales, with an excess of consumption of 260,000 

 cubic [metres. At the sitting of the 14th, the gas company 

 refusing to accept the price offered to them as a compen- 

 sation for their expenses, proposed to supply the gas gratis, 

 which was agreed to. Consequently a regular competition will 

 be carried on between gas and electricity before the Parisian 

 public during one year, on a gi-and scale, at the expense of only 

 34,044 fr. 



It was recently affirmed in the French Academy that chromic 

 acid might be substituted for vanadic acid in the manufacture of 

 aniline black. An industrial chemist of Rouen, M. Witz, now 

 points out to the Academy (by recommendation of Prof. Girardin) 

 that this is an illusion, and that vanadium is absolutely necessary. 

 Chromium gives a greenish product quite different, M. Witz 

 insists on the small quantity of vanadium which suffices to develop 

 the reaction. It appears that the black is produced in presence 

 of a weight of vanadic acid equal to only the hundred millionth 

 part of the weight of the aniline employed. In practice, a 

 thousandth of this weight is quite sufficient, and it will be seen 

 that notAvithstanding the high price of vanadium, the use of it in 

 such small quantities is quite practicable for manufacture. 



The Anthropological Exhibition which will be held at Moscow 

 next summer promises to be a highly interesting one. A large 

 series of graphic illustrations of the life of prehistoric man will 

 be supplemented by numerous models of caves, skeletons, and 

 other prehistoric objects. So-called "kurgane" (prehistoric 

 tombs) will be represented containing models of (he skeletons 

 and other objects found in them, their various positions being 

 exactly reproduced. Prehistoric skulls will form a separate 

 department of the Exhibition. '' ' •-'- ' - -■ ^ - 



We have received the Proceedings 4^ the Clevelauid Institution 

 of Engineers, containing the address of the president, Mr. John 

 Gjers,^ at the annual meeting of November 11. The address 

 refers to various topics of much interest to engineers and even 



to men of science. Among other things Mr. Gjers, speaking of 

 the variation in the production of the soil, gives it as his opinion 

 that it is undoubtedly connected with the variation in the number 

 of sun-spots. The December number of the Transactions of 

 the Institution of Engineers and Shipbuilders in Scotland con- 

 tains a paper by Mr. James Howden, " On the Action of the 

 Screw Propeller," followed by a long discussion, and another by 

 Mr. W. G. Jenkins, " On the Scientific Form of Harbours as 

 applied to the Port of Melbourne." 



A FOREIGNER, who fears the disappearance of bears in the 

 Alps, the killing of these animals being largely paid for in 

 Switzerland by the State and by the communes, and several wild 

 animals having already disappeared in Switzerland in this way, 

 proposes to form a society which wilLiJ?^ ^^'^ each disaster 

 caused by bears, and prohibit the hunting ^^f them. 



The additions to the Zoological Society's Gardens during the 

 past week include a Macaque '^lovikfj ' {Macacus cynomolgus) 

 from India, presented by Mr. D. Orpen ; a Black-faced Spider 

 Monkey {Ateles ater) from South America, pre ented by Earl 

 Brownlow, F.Z.S ; a Common Seal {Phoca vitulind) from Scot- 

 land, presented by the Earl of Hopetown ; a Dufresne's Ama- 

 zon (Chrysotis dufresniana), a Yellow-Fronted Amazon (05ryj<>//j 

 ochroceJ>hala) from South America, presented by Mrs. T. Smith ; 

 a Noddy Tern (Anous stolidus) from Ascension Island, pre- 

 sented by Morris H, Smyth Long, Lieut. R.N. ; a Tuberculated 

 Lizard [Iguana tuberculata) from the West Indies, presented by 

 Dr. Stradling ; a Superb Tanager {CalHste fasiuosa), a Yellow- 

 winged Blue Creeper {Ccereha cyaned) from South America, two' 

 Merrem's Snakes {Liophis merremi) from Monte Video, .de- 

 posited ; two Cuming's Octodons [Octodon aimingi), born i|» the 

 Gardens. 



B^ 



ON THE LAVAS OF HEKLA, AND ON THE 

 SUBLIMATIONS PRODUCED DURING THE 

 ERUPTION OF FEBRUARY 2T, 1878 



UNSEN in a Memoir "On the Processes which have 

 taken place during the Formation of the Volcanic Rocks 

 of Iceland," published in PoggendorfPs Annalen in 185 1, classi- 

 fies the rocks of the island into two principal groups, which he 

 calls respectively the normal trachy tic, and Xhe normal pyr ax enic. 

 The one possesses the largest proportion of acid, and the other 

 of base, and their composition may be approximately stated in 

 the following analyses : — 



Normal trachytic Normal pyroxenic 



Compo!-iticn. Comoosition. 



Silica 76-67 48-47 



Alumina and protoxide 



of iron 14*23 30*i6 



Lime i'44 ir87 



Magnesia 0*28 6*89 



Potash 3'20 0*65 



Soda 4"i8 i'96 



The trachytic rocks represent a mixture of bisilicates of 

 alumina and of the alkalies potash and soda, %\hile protoxide of 

 iron, lime, and magnesia are almost wanting. On the other 

 hand, the pyroxenic rocks are basic silicates of alumina and 

 protoxide of iron, in combination with lime and magnesia, and 

 insignificant quantities of potash and soda. In the trachytic 

 rocks the percentage of alumina is from 10 to 12, and that of 

 protoxide of iron from 2 to 4; while in the pyroxenic rocks the 

 percentage of alumina is from 10 to 18, and that of protoxide 

 of iron from 12 to 20. Normal trachytic rocks are found in 

 great abundance on the banks of the Laxa, at Laugarfjall, near 

 the great geyser, and at Krafla in the north-ea-t of Iceland. 



The normal pyroxenic rocks are found on and around Hekla, 

 on the banks of the Thjorsa, and at Thingvellir. Bunsen by 

 an admirable induction, supported by a number of analyses, has 

 proved that the rocks of Iceland which do not, closely approxi- 

 mate in composition either to the normal trachytic or the normal 

 pyroxenic, are intimate mixtures of these two classes of rocks. 



