142 



NA TURE 



[Dec. 25, 1873 



vigias of navigators in different parts of the greater oceans. 

 From this and other evidence, I am very well satisfied that not 

 only the Pacific, but also the North and South Atlantic and the 

 Indian Ocean?, are areas of depression. 



Having thus roughly mapped out the world, it becomes an in- 

 teresting problem to correlate the distribution of volcanoes wilh 

 that of tiie rising and sinking land. Tf the older theory of vol- 

 canoes be the true one, that they are the direct results of the 

 eruptive forces of the interior of the earth, we ought surely to 

 meet with them in profusion in those large areas where we know 

 the earth to be relatively rising, M'here in fact the eruptive force 

 of which volcanoes are the supposed violent proofs is concen- 

 trated. Is this so? On the contrary ; and it is this that forms the 

 burden of my present letter. The fact is that we shall search in 

 vain among the large areas of upheaval exce]it along their boun- 

 daries and fringes for any active volcanoes. Tal<e the northern 

 circumpolar region, the most typical area of rising land in the 

 world, and there is absolutely no volcano in it. The Iceland 

 volcanoes and Jan Mayen happen to be outside the area of up- 

 heaval, and in a part of the Atlantic which is notoriously sinking. 

 North America, another large area of rising land, is similarly 

 bare of volcanoes. So is .South Americr, save on the very verge 

 of the Pacific, and that part of the Pacific which I believe to be 

 sinking most rapidly. Australia is probably now rising faster 

 than any area in the world save Spitzbergen, and there we have 

 no volcanoes. Europe is similarly free except in that part of it 

 which is sinking, namely, the Mediterranean border. Lastly, 

 there is the vast continent of Asia, a large part of whose northern 

 surface seems, from all the evidence we can collect, to have been 

 quite recently under water and to be still rising. About Asia I 

 wish to enlarge somevvhat. 



It was one of the peculiar fancies of Alexander Humboldt, 

 the great authority on the Physical Geography of Asia, that 

 there was a large active volcanic region in the Altai Mountains, 

 iScc, and he brought together a great deal of plausible matter to 

 support this view. 



As this volcanic region would be in the midst of one of the 

 largest areas of elevation on the earth's surface, it would conflict 

 materially with the evidence elsewhere and with tlie theory of 

 the distribution of volcanoes for whicli I am arguing. Luckily 

 ior me it has been recently shown, so far as the negative results 

 of those who have been to find Humboldt's volcanoes and have 

 not found them, goes, that is, so fir as the only scientific wit- 

 nesses who have surveyed the region may be allowed to dogma- 

 tise, that Humboldt was entirely mistaken. I will quote the 

 accounts of the Russian surveyors as they have been translated 

 for the Geoyraphical Society. 



" It now remained for me," says Semenof, "to prove by actual 

 observation the existence or otherwise of volcanic phenomena in 

 Djungaria and in the Celestial Mountains, to which Humboldt in 

 his woiks so often alludes. I started on my journey, firmly per- 

 suaded that I should find the conjectured volcanoes, or at all 

 events some volcanic forms, and sought diligently (as Schrenck 

 did on Lake Ala-kul) to establish the correctness of Humboldt's 

 surmises with respect to the existence of volcanic phenomena in 

 Central Asia, by which confirmation I knew a traveller would 

 gain greater credit than by any iticomplele refutation of the sup- 

 position. I was even aware that Humboldt was rather dis- 

 pleased wilh the researches of Schrenck, who clearly showed 

 that the island of Aral-TUbe on Lake Ala-kul was not of volcanic 

 origin. Tlie opinions entertained by Humboldt on the subject of 

 the existence of volcanoes in Djungaria were favourite ones with 

 him, and I regret that I was not able to confirtn his cherished 

 theory. KuUok Peak, another of Humboldt's mistaken volcanoes, 

 was found to have no volcanic origin whatever. The hot 

 springs and the non-congelation of Lake Issyk-kul were not 

 accompanied by any volcanic forms in the Tian Shan ; and 

 furthermore, all the native accounts of plienomena which from 

 their description might be supposed to be volcanic proved un- 

 founded, and were at once disposed of on my examination of the 

 localities where they were declared to occur. Tlie result, there- 

 fore, of my researches on this point was that I became convinced 

 ol the complete absence of volcanoes, typical volcrnic pheno- 

 mena, or even volcanic forms, throughout the Celestial i\Ioun- 

 tiins. It is true that there existed in Djungaria at one period 

 sotie solfatara, or smoking apertures, from which there was a 

 discharge and deposit of sulphur, and that some of these fissures, 

 out of which the Chinese obtain sulphur, emit smoke even at the 

 present day. But a careful inspection of one of the extinguished 

 fits satisfied me that, at all events in that case, tliere was no vol- 

 tan'C affinity. In the neighbourhood of the pits discovered by 



me in the Kater Mountains and in the Hi Valley, I could trace 

 no volcanic forms. . . . The whole process of the formation of 

 sulphur can then in my opinion be reasonably explained by the 

 combustion of some coal seams in this basin, which would at 

 once set at rest the question of supposed volcanic agency. . . . 

 The observation of a single portion of the Tian Shan visited by 

 me cannot serve as positive evidence of tlie absence of volcanoes 

 and volcanic forms in other parts of this mountain chain. My 

 conclusions on this question generally have already been made 

 public in the letter referred to, but I must likewise observe in 

 addition that all Asiatic accounts of phenomena which might be 

 volcanic in appearance should be treated by men of science with 

 great circumspection, as many of these accounts have already 

 proved fallacious. I would here also remark that the impression 

 produced on me personally by Djungaria and the Tian Shan 

 leaves great doubts in my mind as to the existence of volcanoes 

 in this part of Asia ; and as I am the only traveller who has 

 visited the Ti.an Shan, I cannot accept the belief in their exist- 

 ence as an axiom requiring no proof or confirmation. My con- 

 clusion on this point, though only negative, is one of the most 

 important results of my journey." {" Djungaria and tlie Celestial 

 Mountains," by P. P. Semenof, Journal of the Royal Geographical 

 .Society, 35-213.) Again, I will quote a later traveller, Mr. Sever- 

 kof. He says — " There are no volcanic formations in the western 

 portions of the Tian Shan which I surveyed. From eastern sources, 

 Humboldt refers to evidences of volcanic action farther south 

 in the Ak-tan, but even these are doubtful. Fire may be pro- 

 duced in the mountains even by the ignition of tlie seams of coal 

 as well as of the c.arburetted hydrogen gas filling the caverns of 

 the seams. This conjecture is supported by the circumstance 

 that Messrs. Bagaslouski and Lehmann discovered, on tlieir jour- 

 ney to Bockhara, a burning seam of coal in the mountains of the 

 upper Zaraphan, a little to the south of the, Ak-tan. Speaking 

 generally of volcanic action in the Tian Shan and the surround- 

 ing regions, the geological surveys hitlierto made from Khan- 

 tengir (east of Issyk-kul, near the sources of the Tonta, Djerga- 

 lan, Tekes, and Kegen) to the extreme western limits of the 

 system, have given only negative results. To the east of Khan- 

 tengir theie are again seams of coal — for instance, at Kuldja, 

 and perhaps also at Urumchi — the ignition of which is quite 

 sufficient to create explosive gases. Whether the seams of coal 

 were ignited at Urumchi by volcanic agency, or accidentally at 

 their denudations, is a question that cannot be settled without 

 close observation. It can only he said that the demonstrations 

 in favour of volcanic action adduced by Hnmboldt are not suffi- 

 cient proof of the volcanic origin of the Tian Shan, excepting 

 only as regards the lava which, according to Chinese records, 

 flowed from the Peslian mountain during the 6th century. But 

 a single crater — even if the fact of its existence in an extensive 

 mountain system extending, as the Tian Shan does, for 3,000 

 versts, can be proved — does not make the whole of the range 

 volcanic. (Severkof's "Journey to the western portion of the 

 Tian Shan," Royal Geographical Journal, 40, 395-6,) 



This evidence, to my mind, completely refutes Humboldt, 

 and makes it very clear that his volcanic region is non-existent. 

 Witli the disappearance o! this, disappears the only exception I 

 know to the rule that volcanoes, instead of being found cliiefly 

 on areas of elevation, are invariably found in areas of depres- 

 sion, or on or close to the boundary lines which separate them 

 from the areas of elevation. The meaning of this lesson, as I 

 read it, I will reserve for another letter. 



In conclusion, I wish to thank one of your correspondents in 

 Tasmania for the fact he communicated to you about the rise of 

 that island. I shall be very grateful to anyone who will send 

 me other facts about areas of upheaval and subsidence, and their 

 communications shall be cheerfully acknowledged when I publish 

 them. 



Derby House, Eccles He.nry II. Howorth 



Spectra of Shooting Stars 



It may interest observers of shooting stars who attempt to 

 obtain views of their spectra by the use of suitably adapted 

 meteor-spectroscopes to indicate a jieculiarity which seems to 

 distinguish the larger meteors of the December star-shower, 

 radiating annually from the direction of a point near 9 Gemi- 

 norum on the nights of the loth, iitb, and 12th of December. 

 Two such small bolides of this stream which appeared to me on 

 December 9th, 1S64, and on Thursday night last, the nth inst., 

 were characterised by a beautiful p.ale-green colour, like that of 



