538 



NATURE 



{_April I, 1884 



Table V. 



On the valuable isochasme chart, in which Prof. Fritz has 

 denoted the increasing frequency of the aurora borealis north- 

 ward-, the maximum zone of the phenomenon falls far soulh of 

 Iceland. I must, however, first explain what my definition of 

 the word maximum zine is at present It is a line passing 

 across the places where the aurora not only appears and is most 

 frequently visible, provided the weather permits, but where it 

 also, as a rule, appears in zenith, or as often on the northern a% 

 the southern hemisphere. According to this definition, the 

 correctness of which I think can neither be di^-puted r.or doul ted, 

 Iceland lies, at all events this year, as w as the case with 

 Kautolieino and Bos^ekop last year, considerably south of the 

 maximum zone, which is, in fact, clearly shown in Table V. 



I hope to be able to demonstrate this in a more conclusive 

 manner still on a future occasion, when the winter is over and 

 the numerous exact determinations of the southern border of 

 the aurora borealis will be discussed. 



The reason why the maximum zone lies so far south on Prof. 

 Fritz's chart may be sought, perhaps, in the circumstance that 

 the climatic conditions of Iceland to a great extent reduce the 

 number of aurorje which an ordinary observer, who only casually 

 or on particular occasions looks at the sky, may observe. That 

 the maximum zone of the aurora does not really fall across the 

 part shown in the chart is also distinctly apparent from what I 

 learnt of its appearance at the Faroe Islands duiing my sojLUrn 

 there. 



It m.ay perlaps be superfluous to state that neither here nor 

 in any other place have I heard the mystic anroral sound. 

 Neither has it ever been heard by any of the Icelanders I have 

 as yet met w ith. 



Shortly before leaving Copenhagen last autumn I spoke w ith 

 a celebrated Danish savant, who had some years ago spent some 

 time in Reykjavik-, and v ho told me tlat he had on several 

 occasions seen aurorae descend below and in front of ihe moun- 

 tain Esja, about 2500 feet in height, and lying six to seven 

 English miles away (Nature, vol. xxix. p. 337). I was de- 



lighted with the prospect of being able to see a similar phe- 

 nomenon, as, although my observations in the plane Bossekop- 

 Kautokeino, previously referred to, had greatly contiibuted to 

 strengthen my belief in the height of the aurora borealis being 

 100 km. or more above the earth (Nature, vol. xxix. p. 412), I 

 would with pleasure have accepted a proof so tangible pointing 

 in arother direction. I regret to say that my expectations have 

 not been fulfilled. This is not because the aurora has not been 

 in close proximity to Esja, a<, the mountain lying to the 

 north-east from this place, nearly all arcs and bands rise with 

 iheir eastern end up behind and run above it, but never have I 

 been so fortunate as to see any auroral light descend to Ihe top of 

 the mountain or in front of its steep sides. Even the highest- 

 lying clouds are also, in Iceland, below the plane of the aurora 

 borealis. 



In conned ion with this point I may further mention that the 

 faint luminosities referred to by Prof. Lemstrom above the 

 mountain-tops at Sodankyla, and in other places (Nature, 

 vol. xxvii. p. 322), as well as phenomena of a similar nature 

 have, I venture to assert, never been observed here. I have 

 continually had my attention directed to this point, and there are 

 several mountains here, but I have never been able to trace the 

 slightest indication of such a phenomenon. 



I brought with me the necessary apparatus and appliances for 

 effecting such experiments as Prof. Lemstrom pursued on some 

 mountains in Northern Finland for the production of an artificial 

 aurora borealis, and shortly after my arrival I came to the con- 

 clusion that the above-mentioned mountain Esja was the most 

 advantageous for such. Its great height, steep fall into the sea, 

 and short distance from the town, were advantages such as no 

 other spot in the district offered, but as I only brought with me 

 1000 m. of insulated wire — telegraph-poles with insulators 

 cannot be employed in consequence of the nature of the ground 

 — and w ished to conduct the wire from the top of the mountain 

 down lo the sea at its foot, I was obliged to wait until I obtained 

 more wire by the steamer at the end of November. Since then 

 the execution of this plan has been attempted a numbtr of times; 

 men, boats, and horses have been ready, and everything pre- 

 pared, but every time the unfortunate weather has frustrated the 

 same. Even in the middle of summer the Esja is a mountain 

 difficult to ascend, and at this time of the year it would be very 

 dangerous to undertake an ascent with the heavy wires, insu- 

 lators, and poles, without the weather being remarkably quiet 

 for several days, 



I intend, however, very shortly to make another attempt, and 

 should this fail I will select a more distant but much lower and 

 more unfavourably situated mountain-top. I will only add that 

 a few days after my arrival I fixed one of Prof. Lemslrom's 

 "utstromnings" apparatus — with 200 points — on the flat roof 

 of a stone tower, 30 to 40 feet in height, and which lies free and 

 isolated on a height in the vicinity of the town ; but the same 

 has up to the present, in spite of numerous trials, given no result 

 whatever. Any current between the points and the earth cannot 

 be traced, and of any luminous phenomena above them there has 

 not been the faintest appearance. Sornus Tromholt 



Reykjavik, February 



ON THE NATURAL AND ARTIFICIAL 

 PERT I LIS A TION OF HERRING O VA 1 

 TN 1862 Prof. Huxley arrived at the conclusion that herring 

 visit our shores in order to spawn twice a year, some schools 

 arriving during the autumn, whde others make their appearance 

 during the winter. The herring which spawn during the autumn 

 chiefly frequent banks on the east coast, while those which spawn 

 during winter are most abundant on the west coast. A report 

 of the Scottish Fishery Board referring to the east coast spawning 

 beds w as published in Nature on November 29 last. The present 

 paper deals chiefly with the Ballanfrae spawning bed, which lies 

 off the co.ast of Ayrshire. 



In 1862 Prof. Allman made some investigations for the 

 Scotti-h Fishery Board, and succeeded in dredging and hatching 

 what was considered herring ova ; but since then, although im- 

 portant results have been obtained by the German and American 

 Commissioners of Fisheries, little or nothing has been done in 

 this country. 



When examining Ihe Ballanfrae Bank the author of thii paper 

 succeeded in dredging several specimens of herring ova attached 



■ Abstract of a paper read by Prof. J. Cossar Ewart, M.D., at the Royal 

 Society, March 27. Communicated by the .Author. 



