224 



NA rURE 



[Jan. 6, 1887 



of the glass. I hope he will excuse me if I point out that in 

 this he hardly does me justice ; for, although words in the above 

 sense are to be found on p. 18, they occur only towards the end 

 of the preliminary treatment of the subject, attention is at once 

 called to the objections to the method, and they are followed by 

 a full account (with references to diagrams) of the method of 

 adjusting the supplies of air and gas so as to produce flames 

 within w/iich lead-glass may be sufficiently heated without 

 reduction. 



I have ventured to trespass on your space to this extent, 

 because, for various reasons, I have come to the conclusion that 

 lead-glass is distinctly the best glass for beginners to work with, and 

 therefore I am anxious to correct the widespread and mistaken 

 idea that its manipulation is very difficult, and requires special 

 appliances. W. A. Shenstone 



Clifton, December 28 



Pyrometers and Fusion-Points 



I READ with much interest the letter from Naples of Dr. 

 H. J. Johnston-Lavis, and beg to offer a few suggestions in 

 answer to his inquiries. I have done much work with pyro- 

 meters, and for my purposes have used Siemens's water pyro- 

 meter with satisfaction. 



It occurs to me, however, that the pyrometer most suitable 

 for the volcanic lava investigations proposed by Dr. Johnston- 

 Lavis would be either Siemens's electrical pyrometer, or the one 

 recently introduced by Messrs. Murries and Co., 45, West Nile 

 Street, Glasgow. It would seem that, with the latter, observa- 

 tions can be readily taken at a considerable distance from the 

 pyrometer, so that the pyrometer stem might possibly be lowered 

 into the crater, and readings of tlie internal temperatures taken 

 at various depths, and possibly of the contained lava also. 



With regard to the fusing points of various substances, refer- 

 ence may be made to the recent careful researches on this 

 subject of Dr. Thomas Carnelley and Prof W. C. Williams. 



Thos. Andrews 



Wortley Iron Works, near Sheffield, January 4, 1S87. 



Electricity and Clocks 



The exact combination about which Mr. Wilson inquires is 

 already in existence : it can be seen at 2, Garfield Buildings, 

 Gray's Inn Koad, in the Jensen electric bell factory. The 

 arrangement used by Mr. Jensen — and it seems to me preferable 

 to that suggested by Mr. Gardner — is to cause the hammer of 

 the small clock to make electric contact in the circuit ^of the 

 distant large bell as it rises in preparation for striking the blow 

 upon its own small bell. With a rnbbin^j contact the action is 

 perfectly certain. Silvanus P. Thompson 



City and Guilds Technical College, Finsbury 



Barnard's Comet 



On December 25, about 6h., with a binocular field-glass, 

 power about 4, I noticed a third tail to this comet between the 

 other two. It was extremely faint, but 6" long, reaching to 11 

 Aquike. The principal tail was reduced to 10° in length, and 

 was far more conspicuous than this shorter, though much 

 broader, tail. The shortest tail, though actually much brighter 

 than this latter, was very indistinct with tliese field-glasses, 

 being best seen with the telescope, power 20, whereas the middle 

 tail was not distinctly visible therewith, although it showed an 

 evident dark space immediately preceding the principal tail. 

 With the naked eye I could see the long tail only. The head 

 was about as bright as S Aquila?. T. W. Backhouse 



Sunderland, December 29, 1886 



Meteor 



I HAVE just seen a very beautiful meteor about the size of 

 Sirius. The local time was within a minute or two of half-past 

 10. It started out between Pollux and the star-cluster in Cancer, 

 and fell rather slowly in the direction of Regulus, going out 

 before it reached that star. It had a trail, which vanished with 

 it. The sky had just cleared after a thunderstorm. 



Sidmouth, December 28 J. M. II. 



Red Sunsets and New Zealand Eruptions 



New Zealand eruptions have not the projectile force to 

 cause red sunsets. Singularly, the very same current of ideas 

 expressed by Prof. Newcomb in Nature, vol. xxxiv. p. 340, 

 occurred to the writer, when in Australian waters the June 

 previous, on the deck of the P. and O. steamer Ballaarat, off 

 the Great Bight, on noticing a peculiarly red northerly sunset. 

 The newspapers at King George's Sound were full of accounts 

 of the magnitude of the eruption of Tarawera, and it must be 

 the fine dust from New Zealand that has passed overhead. 



The atmosphere of Australia, it miy be mentioned, is one of 

 the clearest, "exceptionally free," as Prof. Newcomb puts it, 

 "from vapours or other attenuated matter," and in which 

 volcanic dust would tell immediately. 



This suggestion disappeared at once on getting to the actual 

 site of the New Zealand eruption, only six weeks after it had 

 occurred, and on seeing the limited area covered with mud — a 

 mere nothing compared with the vast stretch of country in the 

 North Island passed through. As there was not a trace of its 

 effects till within eight miles of the foot of Tarawera, it was 

 simply ridiculous to suppose that any of the dust had invaded 

 the higher atmosphere. 



Besides this, the boundaiy of the cloud of atmospheric dis- 

 turbance was distinctly seen, and the altitude placed by none of 

 the spectators to be above 12,000 feet. 



The explosion at Tarawera appears to have been merely one of 

 .'uperheated steam. It was different in the case of Krakatab, 

 where the initial force had much more of the character of an 

 explosion of nitroglycerine than of high-pressure steam, as the 

 matter was stated to have been projected at least 40,000 feet into 

 the air. 



The magnitude of the New Zealand eritptioa could only be 

 felt after getting well within the diameter of sixteen miles on 

 which the mud fell, plastering hill and dale, evenly, of a dull 

 gray, eighteen inches thick. Exterior to this it possessed none, 

 and the distant results evidently were infinitesimal. 



The writer also saw the "green sun " from the south of India, 

 where it lasted for days, and has no doubt that this phenomenon 

 was due to the dust from Krakata~o, such an appearance having 

 never been even faintly approached, before or since, from ordin- 

 ary natural causes, and more impressive, because unaccounted 

 for, than a total eclipse of the sun. 



India, November 26, 1886 A. T. Fraser 



THEODOR VON OPPOLZER 

 npHEODOR VON OPPOLZER, one of the most 

 ■'■ eminent of modern astronomers, died at Vienna on 

 December 26, 1886. He was the only son of Johannes 

 von Oppolzer, the famous pathologist of Vienna, and was 

 born on October 26, 1S41. In accordance with the wish 

 of his father, he studied medicine, and took his doctor's 

 degree in 1S63. From early youth he had shown great 

 interest in astronomy, and, soon after taking his degree, 

 he caused an observatory to be built at his own expense, 

 and resolved to devote himself wholly to his favourite 

 science. In 1S66 he began to lecture at the University 

 of Vienna, on theoretical astronomy, and he was soon 

 promoted to the position of full Professor in his depart- 

 ment. In 1870 he was asked by his Government to 

 take charge of the operations for determining the length of 

 a degree in Austria, and to this task he applied himself 

 with so much energy that all the necessary observations 

 were by and by completed, although his results have not 

 yet been published. 



Oppolzer distinguished himself in all departments of 

 astronomical science. One of the most important of his 

 writings was his " Lchrbuch zur Bahnbestimmung der 

 Kometen und Planeten," a work which has already be- 

 come classical. He had hoped to place the theory of the 

 moon on a new basis, but his labours in connection with 

 this subject were not finished at the time of his death. 

 On his death-bed he corrected the last proof-sheets of 

 his " Canon der Finsternisse," in which he calculates all 

 the eclipses of the sun and moon which have taken place, 

 or which have yet to take place, between the years B.C. 

 1500 and A.D. 2000. 



