Jan. 23, 1879] 



NATURE 



281 



ani that hence in all probability there are but two separate 

 volcanic foci. 



Dr. Genth examined the various lavas from the western slope 

 of HekLa, amonj them the lava erupted in 1845, which was 

 found to contain — 



Silica 



Alomiaa and protoxide of iron 



Lime ... 



Magnesia 



Potash 



Soda ... 



5676 



27 "47 



675 



4" 04 



263 



2'35 



lOO'OO 



The lavas of Hekla are trachytic rather than pyroxenic. In 

 the geological map of Iceland which appears in von Leon- 

 hard's VtUkanen Atlas, a broad strip, including more than half 

 the area of the island, is designated trachyte. It is inclosed by 

 lines running approximately north-east by south-west, — ^that on 

 the west from Skjalfandik to Reykjavik, and that on the east from 

 Heragfloi, to the Orcefa Jokull. 



I was surprised when I visited the scene of the eruption of 

 February 27, 1878 {vide Nature, vol. xviii. p. 596), to find 

 how precisely the lava of this eruption resembled a ver>- old 

 lava in close contiguity to it, but flowing from a distant crater. 

 Moreover the lava of 1845, o'^ the other side of the mountain, 

 and more than four miles Irom the craters of 1878, was observed 

 to be quite the same in character as the most recent lava, which 

 undoubtedly possesses a composition differing but little from 

 that of the analysis given above. 



The most notable feature of the last eruption appears to be 

 the quantity of hydrochloric acid evolved from the beds of lava, 

 and the considerable sublimations of sesquichloride of iron. 

 Bunsen asserts that hydrochloric acid plays a less important 

 part in the volcanic phenomena ol Iceland than at Vesuvius and 

 Etna. 



"The hydrochloric acid fumaroles," he writes, "which not 

 unfrequently occur on a large scale near the Italian volcanoes, 

 and are then generally accompanied by a very considerable sub- 

 limation of chloride of sodiiun, appear to be of less importance 

 in Iceland. I was only able to detect traces of hydrochloric 

 acid in a free state in the crater fumaroles a few months old, 

 which owed their origin to the last eruption of Hekla " (in 

 ^845)> "^ well as in the exhalations of vapour from the lava 

 which was then erupted. " 



For the future we must recognize hydrochloric acid as one of 

 the products of the volcanic action of Hekla. During the last 

 eruption it was produced in considerable quantity. 



I had not proceeded far by the side of the lava of 1878, 

 erupted five months previously, before I saw patches of brilliant 

 red and yellow sublimations on the lava. These I naturally 

 mistook for sulphur, but on a closer approach, warm vapours of 

 hydrochloric acid were found to be issuing from the lava, and the 

 sublimations when removed from the lava speedily deliquesced, 

 forming an intensely acid and corrosive solution of sesquichloride 

 of iron. I only succeeded in bringing one specimen of this sub- 

 limate to England, and this can scarcely be wondered at, when 

 we remember that it had to be carried over 150 miles of very 

 rough and pathless country before reaching the sea-coast. More- 

 over, as iU-luck would have it, the pony which was carrying my 

 minerals, took fright during the last hour of a journey of many 

 days, and within a few miles of Reykjavik our final destination ; 

 the box containing the specimens was broken to pieces, and 

 they were scattered on the groimd, but fortunately without 

 muich injury.. 



The specimen of chloride of iron sublimate has been qualita- 

 tively analysed in our school laboratory, by H. M. Elder, who 

 fiiids it to contain in addition to sesquichloride of iron and free 

 hydrochloric acid, chloride of aluminium, and very small quan- 

 tities of llie chlorides "of ammonium, sodium, and calcium. 

 , During our journey to the scene of the eruption of 1878, we 

 frequently saw large patches of this subhmate, and near one of 

 the new craters, in an inaccessible portion of the lava field, an 

 area of several hundred square yards was covered with it. 

 Most clearly therefore a notable feature of the eruption of 

 1878 has been the emission of large quantities of hydrochloric 

 acid. 



The formation of this substance during the eruption is easy to 

 account for. Sublimations of a white substance were frequently 

 visible in the crevices of the new lava. These, according to 

 Herr Nielssens of E>Tabakki, consist of chloride [of sodium. 



not of chloride of amraoniunu Professor Silvestri found in 

 different sublimations in the lava of Etna, erupted in 1865, 

 quantities of chloride of sodium which varied from 50 to 90 per 

 cent. (/ Fenomeni vulcanici presentati dairEtna nel 1863-6, 

 p«ge 139-142). Chloride of sodium, if it be heated in contact 

 with silica and steam, undergoes decomposition, silicate of 

 sodium and hydrochloric acid being Conned. Bunsen has 

 pointed out the fact that hydrochloric acid fumaroles can only 

 exist when the high degree of temperature necessary for the 

 decomposition of the chloride of sodium, has not receded far 

 below the surface. For if it has so receded, the hydrochloric 

 acid before reaching the surface will necessarily act upon the 

 contiguous rocks, with the formation of chlorides which do not 

 possess a sufficient degree of volatility to be brought to the 

 surface. In the case of the sublimations in the lava of 1878, I 

 noticed both free hydrochloric acid and sublimated chlorides, 

 but the former was small in quantity, and no doubt the subli- 

 mations are receding deeper into the mass as the lava cools, and 

 the next observer may find no trace either of the hydrochloric 

 acid, or the sublimate of sesquichloride of iron. 



G. F. RODWELL 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 



In addition to the regular com-se of instruction in the principles 

 and practice of weaving at the Weaving Branch of the Glasgow 

 Technical Collie, the Directors have made arrangements for 

 three special courses of lectures which are now in course of deli- 

 very. These comprise a series on the history and development 

 of the power loom, by Mr. John Watson, author of a 

 "Treatise on Weaving'"; another on Dyeing, by Mr. Noble; 

 and a third series on Vegetable Fibres, by Air. James Baton, 

 F.L.S., Curator of Kelvingrove Museum. 



The Government of St. Petersburg, as we learn from the 

 annual report just issued, had on December I, 1878 (exclusive 

 of the capital) 53 primary schools of the Ministry of Public 

 Instruction, with 2,262 boys and 1,022 girls; 295 schools de- 

 pending upon the School Boards, with 10,023 boys and 3,519 

 girls, and 21,975/. yearly expenses ; and about 30 schools of 

 separate institutions, with 1,380 boys and 1,533 girls. 



We learn that a Russian lady, Mme. Berladskaya, has just 

 received the degree of Doctor of Medicine at the University of 

 Paris, after having defended at a public meeting her thesis, 

 " On the Structure of Arteries." This paper was spoken of in 

 the highest terms by Prof. Charcot. Mme. Berladskaya is the 

 second lady who has received the degree of Doctor of Medicine 

 at Paris, the first having been Mme. Goncharoff. 



SCIENTIFIC SERIALS 



The Proceedings of the Unnean Society of New South Wales. 

 Vol. ii. part 4, and vol. iii. part I. Part 4, vol. ii. contains : 

 Prof. R. Tate, descriptions of three new species of helix from 

 South Australia ; Rev. }. E. Tenison- Woods, on the extra- 

 tropical corals of Australia, three plates ; the same, on the 

 Echini of Australia, supplementary ; W. Macleay, on the fishes 

 of Port Darwin, four plates ; John Brazier, on the moUusca of 

 the Chevert expedition; the same, on some recently- found 

 mollusca from Port Jackson and New Caledonia ; E. P. Ramsay, 

 on a new species of Rhipidura and of Eopsaltria from the 

 Rockingham district, with remarks on some rare Queensland 

 birds ; the same, on a specimen of Arses tdescophthalmus, on 

 Arses kaupi, and on the young of Cracticus quoyi ; the same, 

 note on Casuarius australis, one plate ; W. Stephens, the 

 President, the annual address. Part i, vol. iiL contains : E. P. 

 Ramsay, on a new species of Ptilotis from Torres Straits ; on a 

 species of Myolestes from Fiji ; notes on list of Australian birds ; 

 and descriptions of five new species of birds from Torres Straits 

 and New Guinea ; Rev. J. E. Tenison- Woods, on an Australian 

 variety of Neritina ptdligera ; on a new genus (Arachnopora) of 

 MiUeporidae ; on a new species of Passamoseris ; on a new- 

 species of Desmophyllum, and on a young stage of Cycloseris 

 sinensis ; on some Australian Littorinidae; W, Macleay, note on 

 a species of Therapon found in a dam at Warialda ; on some 

 new fishes from Port Jackson and King George's Sound ; on 

 a new species of Hoplocephalus ; on the powers of locomotion 

 in the Tunicata ; C. Jenkins, on the geology of Yass Plains ; 

 Count de Castelnau, on the fishes of the Norman River. 



