8o 



NA TURE 



[May 



!2, U 



(see Fig. 2,/) is a short piece of capillar)' glass tubing, to 

 which is fixed a thin sheath of copper, ti, which slides on 

 it, and supports a small plate of polished copper, a', in 

 such a manner that the latter can be held vertically at a 

 small distance from the inner opening of the tube, and so 

 regulate the size of the bubble of air to be directed up- 

 wards into the graduated tube at. 



The apparatus is filled by placing the lower end of the 

 main tube under water, closing the tubes f and i (with 

 caoutchouc tubing and clips), and opening the stopcocks 

 a and d. Water is then sucked in from n, and the whole 

 apparatus carefully filled. The cocks are then turned, 

 and the cut end of the shoot fixed into i, as stated : care 

 must be taken that no air remains under the cut end at i, 

 and the end of the shoot must be at the level k I. This 

 done, the tube /"may then be opened. 



The leaves of the shoot transpire water, which is re- 

 placed through the stem at the cut end in i from the water 

 in the apparatus. A bubble of air passes through the 

 tube /J and at once ascends into the graduated tube«<". 

 The descent of the water-level in this tube — which may 

 conveniently be graduated to measure cubic millimetres — 

 enables the experimenter at once to read off the amount 

 of water employed in a given time. 



It is not necessary to dwell on obvious modifications 

 of these essentials, nor to speak of the slight difficulties 

 of manipulation (especially with the tube/"). Of course 

 the apparatus might be mounted in several ways ; and 

 excellent results for demonstration in class could be ob- 

 tained by arranging the whole on one of the pans of a 

 sensitive balance. H. Marshall Ward 



Botanical Laboratory, 1 (wens College 



AURORAL RESEARCHES IN ICELAND 



TN my last communication to NATURE on the aurora 

 J- borealis in Iceland (vol. x.xix. p. 537), I mentioned 

 that the unusually adverse state of the weather had frus- 

 trated my plan of erecting one of the " utstromnings " 

 apparatus invented by Prof. Lemstrom for the production 

 of the artificial aurora borealis (see Nature, vol. xxvii. 

 p. 389) on Mount Esja, 2500 feet in height, and about two 

 geographical miles north-east from Reykjavik. 



The greatest part of February passed too without show- 

 ing any improvement, and the prospects of getting the 

 apparatus in working order on the mountain whilst the 

 Arctic night still reigned became smaller and smaller. 

 Although 1 regretted this, the study of the aurora which I 

 had observed during the winter had, as indicated in my 

 last communication, gradually convinced me that such an 

 apparatus, even at a greal height above the level of the 

 earth, would, .it .ill events in this part of Iceland, give but 

 a negative result. 



In spite of the favourable position of the island, the 

 electrical ton es, for which the aurora borealis is a visible 

 indicator, appear to possess exceedingly little ene 

 intensity here, which has particularly been the case during 

 the past few months. In consequence I came to the con- 

 clusion that should even all my arrangements be carried 

 out to perfection there was little prospect of producing 

 the " artificial " aurora borealis here. 



On February 22, however, a change in the weather set 

 in, and we had a few lovely days with a clear sky, no 

 wind, and a pleasant temperature. Now, if ever, the time 

 had 1 ome for realising my plan ; and as the weather held 

 for three entire days I fixed the departure for noon of 

 the 25th. 



I was fortunate enough to be able to make the journey 

 in pleasant company, two of the burghers of the town 

 and two Englishmen engaged at some sulphur mines in 

 the vicinity volunteering to accompany me to the top of 

 the mountain. We started at about 10 a.m. in a large 

 sailing boat, with the poles, wires, and the rest of the 

 apparatus. 



In about three hours we] landed at the foot of Esja, 

 and took up our quarters in the farm Mogilsau, from 

 whence I despatched the crew in every direction to call 

 up all able-bodied men to assist in bringing the materials 

 up to the top. Already the same afternoon I had ten of 

 the poles carried up to a height of about 1500 feet. 



The next morning broke clear and fine, promising a 

 day as fine as the previous one. I had then sixteen men 

 at my disposal. They began work at 6 a.m., carrying the 

 heavy things up the mountain, and at 9 the last were 

 taken out of the boat, and we all followed upwards. 



We ascended from the southern side of the mountain 

 about two miles in length. Only now and then we found 

 snow, else the ground consisted of sand and gravel mixed 

 with boulders. The incline is not very great at first, but 

 at times hills and ridges are encountered which tax the 

 muscles and the lungs severely enough. However, the 

 first 2000 feet of the road were not difficult or dangerous ; 

 in fact the only part which could be called so were the last 

 500 to 600 feet. Here the mountain rises abruptly 

 (Esja is formed in terraces), and was covered with a thin 

 layer of snow having a dangerous ice-coating. It was 

 impossible to proceed here without first having hewn 

 steps in the ice. 



At 11.20 we mounted the crest of Esja. The moun- 

 tain stretched snowy-white to all sides as level as a 

 floor. It brought to my mind my ascent of the North 

 Cape last summer. There was a slight breeze blowing 

 which made the air feel chilly. The thermometer showed 

 in the sun at 1 p.m. - 12, at 2 - o'2", and at 3, in the 

 shade, - 3'2° Cels. 



Every hand now became busy with erecting the 

 apparatus. The layer of snow on the surface of the 

 mountain was not thick enough to support the poles, and 

 as the ground was frozen hard, they were — thirty-one in 

 number — raised in cairns of large boulders, of which there 

 were great quantities on the edge of the plateau. The 

 poles being raised, the copper wires, along which there 

 were fixed more than a thousand fine points, were sus- 

 pended over the insulators on their tops. The wires were 

 850 feet in length, and the poles were erected in such a 

 manner that square spiral slings were formed, being a 

 distance of 6 feet from each other. The total surface area 

 of the "utstromnings" apparatus is therefore 4100 square 

 feet. 



The work of erecting the apparatus occupied about four 

 hours, and from the four barometrical \ observations I 

 had an opportunity of making during the time — in con- 

 junction with those which were, at my request, simul- 

 taneously, and with a similar instrument, effected at 

 Reykjavik — I have fixed the height at which the appa- 

 ratus stands at 2616 feet. 



At 3.30 the descent began. The first part of this was 

 far more risky than the ascent, as the steps cut became 

 worn down and new had to be made. Simultaneously a 

 very strong copper wire, carefully insulated by layers of 

 canvas and indiarubber — the insulation being 6 mm. in 

 diameter — was brought down the mountain by the shortest 

 road, as far as it reached. 



The next morning welcomed us with wind and heavy 

 clouds, with a rapidly-falling barometer. The remaining 

 poles were now brought up the mountain, and the bare 

 telegraph wire, 3200 feet in length, carried to the spot 

 where the insulated conductor ended. Both wires were 

 connected in the most careful and exact manner, and the 

 bare wire laid down as an ordinary telegraph wire on 

 poles with insulators as far as it went. I had expected 

 from its great length that it would reach down to the foot 

 of the mountain, but it did not : it only reached to a 

 height of 714 feet. When the wires in increasing nun 

 and wind were laid out, I connected the end with two 

 zinc disks one of which was placed in a small waterfall 

 with heavy stones on it, and the other buried in the earth. 

 When, finally, 1 had by means of a telephone and [a gal- 



