212 



KNOWLEDGE 



NoVEMDER 1, 18'JS 



reflected by an equal area of snow. According to the 

 measurements of Zollner, clay marl reflects 0-156 of the 

 total light, and dark grey syenite 0-078, or about one- 

 tenth of the Ught which is reflected by a surface of clean 

 snow. Consequently, we may probably assume that the 

 darkest parts of the maria correspond in tint to very dark 

 lavas. 



I would, in the first place, invite the reader's attention to 

 the very ciu-ious dark stream which stretches southward 

 from Piton (Fig. 5) on the Mare Imbrium. It is best 

 seen on Plate II., but will be recognized ou Plate I., and 

 on both the plates in the December number of Knowledge 

 for 181)0. It stretches up towards the Crater Aristillus 

 (Fig. 1), and branches into two streams about halfway 

 between Piton and Aristillus. Judging from its appear- 

 ance, it would seem to be a stream of dark material which 

 has flowed from Piton. There can be no doubt about its 

 existence. It is wel' shown on a photograph taken at the 

 Lick Observatory, now in the Astronomical Society's 

 Library, and on one taken by Dr. Henry Draper, as well as 

 on a photograph taken by Mr. De la Rue. 



Another curious dark marking springs from a broad base 

 on the edge of the Mare Imbrium near to Plato, and 

 stretches in a south-westerly direction towards the crater 

 Piazzi Smyth (Fig. 5). This dark marking is best seen 

 on Plate I., but it is also recognizable on Plate II., and 

 on the plates in the December number for 1890, as well 

 as on other photographs. It appears to be connected with 

 other stream-like dark markings more to the eastward, 

 •which are traceable on Plate I. and also in the two 

 photographs in the December number for 1890. 



I would also invite the reader to study the dark parallel 

 lines ou the crater floor of Archimedes (Fig. 1) as shown in 

 the plates, and the curiously contorted dark structure in 

 the region between Archimedes and the lunar Apennines. 

 The darkest part of this structure is near to the foothills 

 of the Apennines. Its curiously contorted form, and 

 especially its darkest portion near to the foothills, is visible 

 in a great many otherwise inferior photographs. 



It will be noticed that the upper or southern half of the 

 Mare Serenitatis is brighter than the lower half, and in 

 Plate II. it will be seen that the darker region has a 

 fringe-like border di%idiug it from the brighter upper half 

 (see A, B. Fig. 8). This might at first be taken for a 

 photographic defect, but certainly some portions of the 

 serrated dinsion may be detected in other photographs. 

 The bright streak which runs through the Mare Serenitatis 

 in a northerly and southerly direction is recognizable in 

 all photographs. It passes through the crater Bessel 

 (Pig. K), and seems to be a ray from the distant crater 

 Tycho. The dark regions fringing the southern border of 

 the Mare Serenitatis are also striking features — they seem 

 to have sharply defined hard edges ; there are also some 

 curious very dark regions to the north of Hyginus (Fig. 9) 

 which are weU worthy of study. 



Kottcfs of i3oofeg. 



I'nimliir Asironumij. — We gladly welcome this new 

 astronomical monthly periodical, edited by Prof. W. W. 

 Payne and C. E. Willard, of the Goodsell Observatory, 

 Northfield, Minnesota. The first number contains an 

 excellent selection of short astronomical articles, brightly 

 written in popular language, but nearly all of them con- 

 taining something that will interest the advanced student 

 of astronomy as well as the beginner. Prof. Daniel 

 Kirk wood gives a most interesting article on "The 

 Asteroids and their relation to the Planetary System," 

 and Prof. Winslow Upton an excellent introductory article 



on "The Constellations and their History." But perhaps 

 the most interesting of the contents of this first number 

 is an article by Prof. Payne on " Jupiter's Comet Family," 

 illustrated by a diagram showing the orbits of the nineteen 

 members of the Jovian family, from Encke's comet down to 

 Holmes" comet of 1892. The grouping of the aphelia in 

 longitude about the autumnal equinox whore Jupiter is 

 moving most quickly through space, because he is then 

 moving in his orbit approximately in the same direction as 

 the sun and his family are moving through space, comes 

 out very strikingly. If subsequent numbers keep up to the 

 standard of the first, " Popular Astronomy " will form 

 a very valuable addition to astronomical literature. 



On Hail, by the Hon. RoUo Russell. (Stanford and 

 Company, 1893.) A most valuable and interesting book, 

 which brings together a mass of information with regard 

 to hailstorms and hail. It is illustrated by two full-page 

 photographs of enormous hailstones which fell at Richmond, 

 Yorkshire, after the terrific hailstorm of the 8th July, 

 1893. It seems that hailstorms have always a cyclonic 

 character. Raindrops, or aggregations of snow, seem to 

 be carried into the central ascending current, which carries 

 them upward, and at the same time the air is rarefied by the 

 centrifugal action of the storm till it is reduced below the 

 freezing temperature. As the frozen snow or drop increases 

 in size, its gravity tends more and more to overcome the 

 rising current, and it is carried upwards with slower 

 and slower velocity, so that smaller drops are carried past 

 it, and when nearly stationary it increases in diameter 

 very rapidly by blending with smaller drops which come 

 in contact with it. Ultimately it is carried out of the 

 central parts of the tornado, and generally falls in the 

 south-east quadrant of the cyclonic storm. 



Sctcn« Notes. 



— -•■ — —— 



Natural Science criticizes the language of the American 

 biologist. The disease of speculation is growing in 

 biology, but on this side of the Atlantic, though we may 

 have idioplasm^ and ids, things really as unsubstantial 

 as the gnomes who formerly presided over the segre- 

 gation of minerals, we at any rate have nothing like 

 " bioplastology," " phylonepionic," " paragerontic," and 

 " metaneonic," in which to clothe our ignorance and 

 dazzle the common man. Biology certainly displays a 

 very unhealthy tendency just at present to accumulate 

 theories and theoretical names in the place of recording 



and systematizing facts. 



— »-♦-. — 



That familiar friend of the geological beginner, Eozoon 



Canadense, has at last received its ijuietux and must figure 



nevermore in the category of once living things. Drs. 



Johnston Lavis and J. W. Gregory have found eozoon to 



perfection, stolon tubes and everything complete, in ejected 



blocks of metamorphosed limestone from Monte Somma, 



and so the last link in the chain of evidence to prove 



eozoon a merely mineral structure is completed. However, 



the Archseans were not lifeless, for Dr. (Iharles Barrois 



described Archiean Eadiolaria as long ago as last year in 



the Co)iiptes Hendux. 



A red-hot wire of platinum has for many years past 

 been used for cutting various organic substances, but it is 

 stated in the London Chemical News that Mr. Warren has 

 discovered a new use for this method and employs a wire 

 heated by an electric current to saw the hardest kinds of 

 wood. At first the wire would break, but he remedied this 

 by using a steel core platinum-plated by a solution of 

 platinic chloride in ether. 



