378 



KNOWLEDGE & SCIENTIFIC NEWS. 



[March, 1906. 



had both employed electric discharges to cause nitrogen 

 and oxygen to enter into combination, no commercial 

 process had biH'n found practical for the synthesis of 

 nitrates from the air, until recently. 



After referring, in passing, to the tentative processes 

 of Bradley and Lo\ejoy, of Kovvalslvi, of Xaville, and 

 to the cyanamide and cyanide pr<x:esses, attention was 

 directed to the process of Birkeland and Eyde, of 

 Christiania, for the fixation of atmospheric nitrogen, 

 and their synthetic producti(jn of nitrates, bv use of a 

 special electric furnace. In this furnace an alternating 

 electric arc was produced at between 3,000 and 4,000 

 volts, fiut under special conditions which resulted from 

 the researches of Professor Birkeland; the arc being 

 formed between the poles of a large electro-magnet, 

 which forced it to take the form of a roaring disc of 

 flame. Such a disc of flame was shown in the lecture 

 theatre by a model apparatus .sent from Christiania. 

 In the furnaces, as used in Norway, the disc of flame 

 was four or five feet in diameter, and was enclosed in a 

 metal envelope lined with firebrick. Through this 

 furnace air was blown, and emerged charged with nitric 

 oxide fumes. These fumes were collected, allowed 

 time further to oxidise, then absorbed in water-towers 

 or in quicklime — nitric acid and nitrate of lime being 

 the products. The research station near Arendal was 

 described; also the factory at Notodden, in the 

 Hitterdal, where electric power to the extent of 1,500 

 kilowatts was already taken from the Tinnfoss water- 

 fall for the production of nitr.ite of lime. This product 

 in several forms, including a basic nitrate, was known 

 as Norwegian saltf>elre. Experiment had shown that 

 it was equally good as a fertiliser with Chili saltpetre; 

 and the lime in it was of special advantage for certain 

 soils. The yield of product in these furnaces was most 

 satisfactory, and the factory at Notodden — which had 

 been in conmiercial operation since the spring of 1905 

 — was about to be enlarged; the neighbouring waterfall 

 of Svaelgfos being now in course of utilisation would 

 furnish 2-5, oco hor.se-power. The Norwegian company 

 had further projects in hand for the utilisation of three 

 other waterfalls, including the Rjukanfos, the most con- 

 siderable fall in Telemarken, which would yield over 

 200,000 horse-power, .■\ccording to the statement of 

 Professor Otto Witt, the yield of the Birkeland-Eyde 

 furnaces was over 500 kilogrammes of nitric acid per 

 year for every kilowatt of power. The conditions in 

 Norway were exceptionally good for the furnishing of 

 power at exceedingly low rates. Hence the new pro- 

 duct could compete with Chili saltpetre on the market, 

 and would become every year more valuable as the de- 

 mand for nitrates increased, and the natural supplies 

 became exhausted. 



What is at the Centre 

 of the^arth? 



By H. DE .St. I^ai.mas. 



The mystery of this c|Ucstion is assigned as one reason 

 for its investigation. It is, indeed, remarkable that 

 less should be known about the earth's composition, 

 even at the depth of a few niile3, than is known of the 

 composition of stars millions of miles awav. 



In " Know i,ed(;e " for January doubt is cast on the 

 generally accepted theory of .1 regular and sustained 

 increase of heat as the earth's crust is penetrated. The 

 data are not sufficient to establish this theory. The in- 



crease of heat in deep mines and borings has been 

 attributed to the central heat of a gradually cooling 

 planet. How can we know that this is the true cause 

 of the heat at only a mile or two from the earth's sur- 

 face, seeing there is no proof that the fiery heat extends 

 to the earth's centre? 



Reasoning on the effects of pressure at various 

 depths, Mr. lieresford Ingram suggests that the earth 

 may consist of " three concentric rings," having a 

 solid nucleus from 3,000 to 7,000 miles in diameter, 

 next a liquid substratum, and finally the earth's crust, 

 variously estimated at from 70 miles to 2,000 miles in 

 thickness. 



Dr. I-xlmund Halley propounded a similar theory of 

 the earth's composition before the Roval Society in 

 1694. The mysteries of terrestrial magnetism seemed 

 to point to such an arrangement to account for the 

 uniform slow revolution of the magnetic fxile round the 

 pole of the earth. The nucleus (or TcrrcUa) imagined 

 Ijy Halley, though concentric with the main body of the 

 earth, he maintained rotated on a different axis, the 

 axis of the nucleus being indicated by the magnetic 

 poles. Halley considered that the axis of the nucleus 

 was originally that of the entire earth, and that a 

 change of axis had taken place in relation to the outer 

 globe, this being the physical cause of the deluge, as it 

 would necessarilv bring the ocean waters and .Arctic ice 

 over mountains and continents. 



Halley maintained this belief more than thirty years 

 till his death. The late Sir Edward .Sal)ine, speaking 

 Irom the Presidential chair of the Royal .Society in 

 1864, said that " the objections that might ha\e im- 

 peded the reception of such an hypothesis . . are no 

 longer tenable." 



1 he late astronomer royal, Sir George Airy, expressed 

 the opinion " that the general cause of the earth's 

 magnetism still remains one of the mysteries of cosmi- 

 cal physics." The distinguished Lord Kelvin has ex- 

 pressed himself similarly only a few years ago. So 

 that we are now no further advanced in actual know- 

 ledge of the earth's interior and of terrestrial 

 magnetism, than when Halley maintained more than 

 2oa years .igo that " thus and not otherwise " could 

 the facts be explained. 



Halley 's fhetjry of the earth has been popularised by 

 the late Rev. W. B. Galloway, M..\., in " Science and 

 (ieology in Relation to the Universal Deluge" and 

 "The Testimony of -Science to the Deluge." Mr. 

 Galloway shows that the specific gravity of the earth 

 being about 57V times that of water, whilst the rocks at 

 the earth's surface do not average more than ai, it 

 follows that the heaviest substances, such as gold and 

 platinum, should be at the centre, and that mercury or 

 C|uicksilver, in harmony with its specific gra\ ity, might 

 form the liquid substratum between the two differently 

 rotating globes. The arguments — astronomical, geo- 

 logical, climatic, and historic — in support of Halley's 

 and Galloway's theory of the earth are well worthy of 

 examination. 



Whilst astronomers and geologists cannot tell if the 

 earth has a rigid core or a molten interior, the 

 hypothesis of " three concentric rings " should not be 

 regarded as untenable, i.e., an inner and an outer globe 

 with a fluid substratum, such as mercury, petroleum, 

 or molten la\ a (all of which have Ix'en suggested) inter- 

 posed between the TcrrcUa and the outer globe. In 

 such case the heat, which is found to increase in de- 

 scending below the earth's surface, might be caused by 

 the friction of two differently rotating bodies, and not 

 bv imaginary fires at the centre of the earth 



