June 12, 1884] 



NA TURE 



155 



vations which in his opinion demonstrate that in the chain of the 

 Jura, the east of the Paris basin, and in Portugal the lower part 

 and even the whole of the Callovian are locally replaced by an 

 extension of the Bathonian deposits. — (Jornal de Sciencias 

 Mathematicas, &c, Lisboa, No. xxxvii., 1S84.) 



The Glacial Boundary in Ohio. — Prof. G. F. Wright 

 has for ten years past been studying the glacial phenomena of 

 the Eastern States of the Union. Beginning with the kames 

 of the Merrimac Valley in Eastern Massachusetts, he has fol- 

 lowed the last edge of the glacial trail from the Atlantic border 

 across to the southern part of Illinois. How much further he 

 may have to trace it westwards he is at a loss to know. Mean- 

 while he gives an interesting outline of his labours in a pamphlet 

 just issued by the Western Reserve Historical Society of Cleve 

 land, Ohio. The edge of the deposits left by the ice-sheet of 

 the Glacial Period or "terminal moraine," as the American 

 geologists call it, has been traced by him from the western part 

 of Pennsylvania across the southern counties of Ohio and the 

 northern margin of Kentucky to near the Miami and Ohio Rivers. 

 It then enters Indiana and makes a great northward sweep as 

 far as -Martinsville, a little south of Indianapolis, whence it turns 

 south-westwards and passes into Illinois a little above the con- 

 fluence of the Wabash with the Ohio. The Report gives detailed 

 maps of the . " moraine " in its passage across Ohio, with de- 

 scriptions of the nature and form of the drift ridges in the different 

 counties and townships. 



Hyperstiiene-Andesite and Triclinic Pyroxene in 

 Augitic Rocks. — The United States Geological Survey has be- 

 gun the issue of a Bulletin designed to appear from time to time 

 in single parts, each containing a single paper complete in itself. 

 These papers are to be such as relate to the general work of the 

 Survey, but do not properly come within the scope of the Annual 

 Reports or Monographs. The first number is devoted to the rocks 

 of Buffalo Peaks, Colorado. A sketch of their geology by Mr. 

 Emmons, the geologist in charge of the Rocky Mountain Division 

 of the Survey, is followed by a detailed description of some vol- 

 canic masses by Mr. Whitman Cross, in which he continues his 

 interesting researches on pyroxenic rocks. As fragments among 

 the beds of tuff and likewise in place on the shoulder of the main 

 Buffalo Peak, there occur certain augite-andesites the micro- 

 scopic study of which reveals some important peculiarities. The 

 pyroxenic constituent shows that a rhombic mineral, probably 

 hypersthene, is largely predominant, while a great number, if 

 not all, of the remaining crystals must be considered as triclinic. 

 The occurrence of triclinic pyroxene had already been detected 

 by the author among the crystalline schists of Brittany. He has 

 been led to re-examine many pyroxenic rocks (diabase, mela- 

 phyre, basalt, &c. ) from widely separated localities, with the result 

 of finding, in some common rocks from well-known localities, 

 that the augite, when placed between crossed Nicol prisms, is 

 extinguished at a very decided angle from the diagonals of the 

 prism. This abnormal action he thinks must show either that 

 the mineral in question is triclinic or that there is an "optical 

 anomaly." Following the example of Fouque, who isolated 

 and analysed the normal augite and unsuspected hypersthene of 

 the Santorin andesite, Mr. Cross isolated the rhombic pyroxene 

 of the rock of Buffalo Peaks, and proved its crystalline form by 

 examining detached crystals under the microscope. He likewise 

 submitted it to chemical determination, which proved it to be 

 true hypersthene. These researches induced him to test the 

 character of the pyroxenic constituent in other andesites from 

 all parts of the world. He has found that a rhombic pyroxene 

 is much more abundant in porphyritic crystals than augite. He 

 suggests the need of a reclassification of andesite rocks, ofwhich 

 he thinks three main groups may be distinguished. At one 

 extreme are the varieties with a trachytic character rich in fel- 

 spar, often containing quartz or tridymite, and with a more 

 crystalline ground-mass. At the other extreme are some basalt- 

 like masses, but with little or no olivine. The normal " augite- 

 andesites " form the intermediate group. 



KRAKATOA AND THE SUN-GLOWS 



T N the last issue of the Bulletin of the St. Petersburg Academy of 

 -*■ Sciences (vol. xxix. Xo. 2), M. RykatchefF publishes a very 

 interesting paper on the atmospheric waves produced by the 

 Krakatoa eruption. General Strachey and Mr. R. H. Scott 



(Nature, vol. xxix. p. 1S1) have already shown how the erup- 

 tion must have produced an atmospheric wave which has been 

 noticed by the barometers at many meteorological observatories. 

 The wave was propagated in concentric circles, increasing in 

 diameter until it reached the great circle ; then, it con- 

 tracted until reaching a point on the antipode of Krakatoa, 

 whence the wave returned in the same way to its point of 

 origin ; then, gradually diminishing in intensity, it made 

 for a second and third time its way around the earth. M. 

 Rykatcheff now publishes the curve of the barograph of Pavlovsk 

 for August 27 to 30, where the influence of the atmospheric 

 wave is pretty well seen ; and he discusses the results obtained 

 from observations at thirty-one different stations (Pavlovsk, St. 

 Petersburg, Berlin, Leipzig, Magdeburg, Brussels, Paris (I. and 

 II.), Toulouse, Greenwich, Kew, Aberdeen, Stonyhurst, Liver- 

 pool, Glasgow, Falmouth, Armagh, Valentia, Georgia Island, 

 Coimbra, and Toronto). It appears from these observations, when 

 calculated according to Gen. Strachey's method, that is, by taking the 

 time 1 ictween two successive passages of the wave at the same sta- 

 tion, that, for European stations, on the average the wave took 

 30I1. 38m. to make its way around the earth when it was going from 

 east to west, and 3511.54m. when going from west to east. The 

 accordance of the figures for different observatories is striking 

 (excepting Tolosa), the greatest deviation from the average being 

 only + 33m. and - 38m. in the first case, + 27m. and - 39m. 

 in the second. The average speed would thus be : for the first 

 wave, 303-3 metres, and 316-1 metres for the second. The cal- 

 culated time of the Krakatoa eruption would be between c,h. 6m. 

 and 9h. 42m. Krakatoa mean time ; or, on the average, 9I1. 23m. 

 When the calculations are made on M. Wolf's method (which 

 admits the same speed in both directions), the average speed 

 of the wave is 334-3 metres, and the time of the eruption 

 would be ioh. 39m. Krakatoa mean time. Finally, M. 

 Rykatcheff makes the calculations by deducing both speed and 

 time of eruption from observations made at two stations next to 

 Krakatoa (Pavlovsk and St. Petersburg), and then he calculates 

 from equations made for all other stations the error of the two 

 observations. He receives thus 321 '4 metres for the speed of the 

 wave, and ioh. 16m. for the time of the eruption at Krakatoa. 

 These results are more in accordance, he says, with the result 

 obtained by Herr Wolf's method, and, combining both, M. 

 Rykatcheff takes as probable 327-9 metres for the speed, and 

 ioh. 27m. for the time of the eruption. As to the amplitudes 

 of the oscillations of the barometers at different stations, they 

 vary from 0'9 to 17 -mm. and reach 2 '5 mm. at Georgia 

 Island. 



To the Meteor, login-he Zeitschrift for 1884 Dr. G. Hellmann 

 contributes a learned paper on the recent glows. No 

 theory is advanced as to their origin, and the interest of the 

 paper is mainly historical. The oldest reference to similar 

 phenomena the writer has been able to discover is that of the 

 Flemish physician, H. Brucanis, who, in 1570, dedicated a 

 "Tractatus de Crepusculis " to Tycho Brahe. _ In this work 

 occurs the passage : " Cum autem diluculum initium sumat, ubi 

 aer splendescere incipit, idque eveniat cum lumen solis ab ae're, 

 ob vapores permixtos crassiores, versus horizontem reflectitur, 

 patet non in eadem distantia solis ab horizonte crepuscula semper 

 incidere, quod non una sit semper aeris densioris sive vaporum, 

 a quibus fieri possit radiorum reflexio, altitudo." 



In the An miles de Ckimie et de Physique, sixth series, vol. i. 

 1884, MM. Perrotin and Thollon deal with the same subject 

 from the physical standpoint. They give an able resume 1 of the 

 various accounts that have appeared, especially in Nature, and 

 seem on the whole disposed to accept the theory of the volcanic 

 origin of the after-glows. 



A correspondent, F. A. R. R., sends us the following com- 

 munication on the subject : — 



The matter projected into the upper atmosphere appears to 

 have passed round the globe westwards with great velocity, and to 

 have diffused itself towards north and south much less rapidly. A 

 stratum of fine dust thus formed itself at an elevation probably 

 exceeding the altitude of the known upper currents. This 

 stratum caused the sun to look green or blue on the Gold Coast, 

 in the West Indies, at the Sandwich Islands, in India and the 

 Indian Ocean, and last, as late as September 24, in the Soudan, 

 nearly a month after the eruption of Krakatoa. The moon and 

 stars were frequently greenish in Europe in December and 

 January, up to four months and a half after the eruption, 

 'and the sun whiter than usual towards setting. The finely 

 divided matter which thus deprived the sun and moon of 



