May 26, 1887] 



NA TURE 



77 



The Eclipse of August 19, 1887. 



Phis eclipse will be seen over such an extent of territory that it 



lesirable to make the best use of the opportunity offered. The 



ronomical observations I do not mention, but besides them 



; following would be very important, and could be made by 



.vellers alone, and those who do not take with them heavy and 



niblesome instruments : — 



Observations every ten minutes on the pressure and tem- 



■atnre of the air from the beginning of the eclipse to about 



If an hour after its end ; and, some days before and later, 



ery hour, at the hours of the eclipse. 



The barometer might as well be an aneroid, but with large 



visions ; a pocket instrument would be too small. Relative and 



it absolute measures are intended, and it is especially necessary 



at the instrument be not sluggish. 



The thermometer preferable for the observations should be a 



ng-thermometer (Frowde), as one in a thermometer-stand and 



t swung could not follow rapidly enough the changes of tem- 



rature. It would be best to swing it at the height of the 



oulder. 



Observations on cloud, direction and force of zuind, every 



If hour the day of the eclipse and every hour before and 



er. 



Some observations on the colour of the sky, &c., and on 



I influence of the eclipse on animals, domestic and wild, 



)uld be useful. 



The eclipse will be visible in Eastern Germany, but at so early an 



ur in the morning that there will be comparatively little interest 



meteorological observations. Russia (especially Eastern) and 



estern and Central Siberia give much better opportunities of 



servation. I give below some notices on the amount of cloud ; 



; stations are disposed from west to cast, the mean is that of 



ee observations, 7 a.m. , I p.m., and 9 p.m. The conditions as to 



udiness will be better than those indicated here, in Eastern 



issia and Siberia to nearly Lake Baikal, as the eclipse will be 



:n in the later morning hours, which have a smaller amount of 



ud than 7 a.m. and i p.m. 



Amount of Cloud. 



Rjev, Government of Tver 

 Moscow ... 



Academy of Petrovsky, near Moscow.. 

 Rojdestwenskoye, Government of Kos- 

 troma ... 

 Kasan 



Viatka 



Ekaterinburg ... 



Nijnetaguilsk 



Bogoslovsk 



Irbit 



Irbit 



Yeniseisk 



Irkutsk ... 



Foundry of Nertschinsk 



Niigata, west coast of Nippon 



[ give a list of some places where tolerably good accommo- 

 ion is to be found, with the time of travel from the nearest 

 way-station : — 



Tver, Torjok, Moscow,^ Yaroslav,- Kostroma (three hours' 

 imer from latter point), Schuja, Ivanovo-Wosnessensk, 

 leschma, Vladimir, Viatka (steamer on Volga, Kama, and 

 tka, from Nijni-Novgorod, in three days), Perm (steamer 

 n Nijni-Novgorod in eighty-five hours. 



Vijnetaguilsk, with important foundries, malachite mines, &c. , 

 :hed by railroad from Perm in fifteen hours, 

 Tobolsk, by rail from Perm to Tjumen in about thirty hours, 

 nee by steamer in two days, twice a week. It is well to 

 graph beforehand to retain a cabin. 



^omsk by steamer from Tjumen in about eight days, by the 

 a, Tobol, Irtysch, and Ob. 



"he places eastward, the most favourable for observation, can 

 reached by road only from Tomsk. Post-horses everywhere 

 liable, rapid travelling in good weather, but bad carriages. 

 'o astronomers bringing with them bulky instruments, the 

 er-ways are to be recommended. St. Petersburg is in easy 

 mer communication with Briti.sh harbours, and thence 



Just at the southern limit, it would be better to observe somewhat to 

 lorth. 

 See Mackenzie-Wallace's " Russia." 



'ugg^ge can be sent by water to all parts of the Volga basin. 

 So far as known at present, it is intended that there shall be 

 observations of the eclipse at five points : (i) the observatory of 

 General Maiewsky, Government of Tver ; (2) the estate of Count 

 Olsufifiew, district Dmitrov, Government of Moscow ; (3) the 

 estate of Prof. Bredichin, district Kineschma, Government of 

 Kostroma, — two English astronomers are expected ; (4) Glasov, 

 Government of Viatka ; (5) Krasnoiarsk, on the Yenisei. 



A. WOEIKOF. 



Iridescent Clouds. 



The clouds seen by Prof. Stone, as described in Nature, 

 vol. XXXV. p. 581, may have been of the same character (though 

 I cannot judge positively from the description) as those so ex- 

 tensively observed in the Decembers of 1884 and 1885 ; if so, it 

 is the only account I have read of their being seen last winter. 

 Those described by Mr. McConnel, writing from St. Moritz, 

 Switzerland (p. 533), are evidently of a totally different charac- 

 ter, and I suppose simply the ordinary iridescent clouds which 

 are common everywhere. T. W, B.A.CKHOUSE. 



Sunderland. 



Remarkable Hailstones. 



May I ask for space to make a suggestion as to the possible 

 cause of the banded .structure of hailstones recently observed and 

 recorded in Nature, vol. xxxv. p. 438 ? It seems to me that 

 the phenomenon may perhaps be explained by devitrification of 

 the ice. We are familiar with a considerable number of bodies 

 which assume the vitreous state by rapid solidification from the 

 liquid state ; and it seems reasonable to suppose that in the con- 

 ditions under which hail is formed the ice may assume at first 

 the vitreous state, the higher molecular structure of perfectly 

 crystalline ice requiring more time for its full development 

 (see paper by the writer read before Section C of the 

 British Association last year at Birmingham). If such 

 were the case (and the hypothesis is supported by the state- 

 ment of Mr. C. S. Middlemiss in Nature, vol. xxxv. p. 413), 

 the observed structure (which can be actually seen to develop 

 itself in some vitreous substances under the microscope, as a 

 preliminary to the assumption of the full crystalline and opaque 

 condition) would simply mark an early stage of the devitrifica- 

 tion of the iceglass. To bring this theory to the test of experi- 

 ment it would only be necessary to observe closely the effect of 

 keeping such hailstones for some time at a temperature rather 

 below 0° C. A. Irving. 



Wellington College, Berks, May 14. 



The Orbit of the Minor Planet Eucharis.' 



On reading your note (p. 16) on the determination of the 

 orbit of the planet Eucharis, by Dr. de BeiII, and the discord- 

 ances between his observations and those obtained with the 

 Washington meridian instrument, I am reminded of an earlier 

 case which seems to me to be analogous. 



Hansen drew attention to the very material difference between 

 the observations of Egeria in 1864 at Bonn and Leyden. This 

 discrepancy between observations which otherwise harmonized 

 well amounted to 10" in R. A., and occasioned a protracted 

 inquiry by Argelander {Astron. Nachr., No. 1769), in which he 

 came to the conclusion that the reason probably lay in the 

 personal error of the Leyden observer in the observation of 

 bright and faint stars. As I am not acquainted with Dr. de 

 Ball's treatise, I cannot judge whether respect was paid to such 

 differences in isolated cases. W. Valentiner. 



Karlsruhe Observatory, May 8. 



A Question for Chemists. 



Your correspondent, Mr. West, will find reference to the 

 fact that a mixture of glycerine and potassium permanganate is 

 liable to spontaneous combustion in the " Extra Pharmacopoeia " 

 of Martindale and W^estcott, fourth edition, p. 292. 



Dublin. Harry Napier Draper. 



" A Junior Course of Practical Zoology." 



In a recent notice of " A Junior Course of Practical Zoology " 

 (Nature, vol. xxxv. p. 506) the reviewer expresses surprise 



