290 



NA TURE 



[May 6, 1909 



Two plates are devoted to a series of detailed sections 

 of the fragmentary materials as distributed around the 

 volcano, and the conditions that influenced the distribution 

 of such materials are discussed. 



The essential ejecta are shown to be represented by two 

 strata of brown and black scoria that form the base of 

 the great sheet of lapilli which covered the north-east 

 sector of the volcano, and were so destructive to Ottajano, 

 S. Giuseppe, and other towns. These were followed by 

 the still more important and larger volume of the accessory 

 ■ejecta derived from the fragmentation and ejection of the 

 .upper part of the great cone. One-third of that great cone 

 has gone, as can bo seen by the photographs in some of the. 

 ,plates, and a tremendous crater half a mile in diameter 

 and of unknown depth afforded these materials. 



The remarkable photographs of the great cone showing 

 ithis truncation, compared with its original outline and that 

 of the new crater at different dates, make impressive 

 •pictures. Plate V. of the memoir, here reproduced in 

 Fig. 2, will remain as a classical view of the general 

 shape of the cone with its scored sides, and Plate VI. 

 of the details of those remarkable barrancos that are 

 like the pleats in a half-opened umbrella. This scoring 

 ■of the slopes of volcanoes was formerly supposed to be 

 due to aqueous erosion, but is shown in this eruption to 

 'be caused by the slipping down of avalanches of loose 



fragmentary materials piled on the steep slopes of the 

 cone towards the end of the eruption, when the ballistic 

 •energy was unable to throw them farther afield. 



Some remarkable " hollow dykes," first described in the 

 1885 eruption, are given on p. 185, and the mechanism 

 of their formation explained. The author believes they 

 were possibly the canals by which issued the lavas of the 

 •Colle Margherita and the CoUe Umberto. 



The microscopic and other characters of the essential 

 ■ ejecta are illustrated by some plates of photomicrographs. 

 The size of the vesicles, the relative amount of glass, 

 microliths, and state of the magnetite are shown to indicate 

 the position of the magma in the volcanic conduit, the 

 amount of volatile constituents it acquired or lost at 

 ■different depths, and their relationship to the different 

 phases of the eruption. 



The minerals and other eruptive products of the eruption 

 are described in so far as they bear on the interpretation 

 of the eruptive phenomena, but the author avoids petro- 

 graphical and mineralogical details that he considers have 

 no special bearing on the study of this outburst. 



In addition to a large number of reproductions from 

 photographs taken by the author, there are plans, figures, 

 and maps. The last plate is a plan, on the scale of 

 1/10,000, of the modifications wrought in the cone and 

 crater, printed specially for this memoir by the Istituto 

 'Geografico Militare of Italy. 



NO. 2062, VOL. 80] 



TANTALUM AND ITS INDUSTRIAL 

 APPLICATIONS^ 

 'V\7HEN the announcement was made in the year 187S 

 that "the division of the electric light had been 

 successfully accomplished," .nany people believed that the 

 days of lighting by gas had come to an end, and acted 

 accordingly, much to their own disadvantage, for the com- 

 petition of the glovi'-lamp served only to stimulate its 

 rival to new life. Burners of improved construction, 

 regenerative burners, and finally gas mantles, helped to 

 restore to gas the ground it had lost, and until a short 

 time ago even threatened to check the spreading of electric 

 lighting. 



Not only this growing competition of gas, but the 

 universal necessity of cheapening 'the production of com- 

 modities that are for general use, forced' electrical 

 engineers to study in all its aspects the question of 

 improving the efficiency of electric lighting. As a guide 

 in their researches they had the well-known principle that 

 the illuminating power of a solid body increases at a 

 much greater ratio than its temperature, or, in other 

 words, that with the increase of temperature a greater 

 percentage of the energy expended for heating the body is 

 converted into light. There is plenty of room for improve- 

 ment, for even the most economical source of light, the 

 electric arc lamp, converts only about i per cent, of the 

 energy of the electric current flowing through it into light, 

 the rest appearing as heat, so that in reality all methods 

 of lighting devised by men are to a much greater extent 

 methods of heating. 



The first successful incandescent lamp consisted of a 

 carbon filament, and for a long time carbon appeared to 

 be the only suitable substance, although the temperature 

 to which such a filament can be raised is limited to about 

 1600° C, as above this point the carbon begins to dis- 

 integrate rapidly. At this temperature the lamp consumes 

 from three to three and a half watts per candle-power, 

 while any attempt to produce light more economically by 

 raising the temperature of the filament results only ii] 

 shortening its life and destroying, thereby, its power of 

 competing with gas lighting. 



An improvement on this result was introduced by Prof. 

 Nernst, of Gottingen, who suggested as the source of light 

 rcfractorv earths, similar in character to those used for 

 gas mantles, which, how'ever, conduct electricity only 

 when they are hot. Lamps constructed on Prof. Nernst's 

 principle have, therefore, to be fitted with contrivances 

 for heating their filaments when starting, which compli- 

 cate the construction of the lamp. 



Another step forward was made by the invention of the 

 osmium lamp, which is produced in a somewhat similar 

 manner to the carbon lamp, by squirting a plastic mixture 

 of metallic oxide and a reducing agent into the shape of 

 a filament, which is gradually heated in a glass bulb by 

 the passage of an electric current, while the bulb is being 

 exhausted by an air-pump or an equivalent device. So 

 far as utilisation of energy goes, these lamps are a great 

 improvement on carbon lamps, but their filaments are 

 very brittle, and the total production of osmium per year 

 is only about 8 kg. for the whole world, of which 5 kg. 

 are required for medical purposes. 



In January, 1905, Dr. W. von Bolton, the head of the 

 chemical Laboratory of the firm of Siemens and Halske, 

 announced in a lecture to the Elektrotechnische Verein 

 of Berlin that he had succeeded in producing pure tan- 

 talum, and his discourse was follow-ed by Dr. O. Feuerlein 

 describing how tantalum had been utilised for filaments 

 in the lamp works of the firm. These discourses pre- 

 sented the result of long years of research work based 

 on the general principle already alluded to, that that fila- 

 ment would give the best economical results which could 

 be maintained for the longest time at the highest tempera- 

 ture. 



The number of substances cap.ible of conducting elec- 

 tricity and of sustaining such high temperatures is verv 

 limited, and platinum, the most refractory of the well- 

 known metals, had been tried and found wanting. It 

 became, therefore, necessary to start the research by 

 ivered at the Roy.il Institution on Friday, April 23, by 



