SCIENCE-GOSSIP. 



34 1 



On the north-west border of the Mart Sertnitaiis 

 there is a fine ring called Posidonius, whose floor is 

 a: a higher level than the plain outside the walls. 

 Near the middle of its floor there is a smaller 

 crater. A, which Schmidt once found without its 

 shadow, and which Schroter once found with a sort 

 of grey veil in place of the shadow. 



Besides these special features, and in many more 

 that could be added, in which there seems evidence 

 of atmospheric phenomena, Professor Pickering 

 has noticed that on observing the moon when 

 near new, the shadows of the mountain ranges 

 always appear fringed with a penumbra ; but 

 although he considers this is evidence in favour of 

 an atmosphere, the density of it cannot be more 

 than that of the earth — at an altitude of about 

 hree miles. 



When the moon's diameter as measured with the 

 micrometer is compared with the diameter deter- 

 mined by the occultations of stars, the measured 

 diameter appears to be about 4- too great. Perhaps, 

 however, irradiation may have something to do 

 with this difference. 



The '• Selenographical Journal" of the former 

 Selenographical Society, from which nearly all the 

 notes given with respect to spectroscopic observa- 

 tions, and also those of Gruithuisen and Schmidt, 

 are drawn, said : " An important observation was 

 made at the Observatory of Melbourne during the 

 solar eclipse of February 2nd, 1878, when the 

 observers endeavoured to ascertain whether the 

 lines of the solar spectrum itself, seen in close 

 proximity to the moon's advancing edge, suffered 



any change or not ; a decided thickening of many 

 of the lines close to the moon's edge was distinctly 

 observed." This observation seems to settle the 

 question with which our paper started, and to 

 answer it with a distinct affirmative. 



There is, however, one more point to be con- 

 sidered. Our moon is not the only one in the 

 system, and those of Jupiter do not differ greatly 

 from it, and at the same time are easy of observa- 

 tion. There seems practically no doubt that, like 

 our own moon, they revolve on their axes once 

 during their orbitual revolution. The mass of the 

 outer satellite is about the same as that of the 

 moon, the third is heavier, whilst the other two 

 are lighter. Notwithstanding this, they all, but 

 most especially the outer, show variations in 

 brightness absolutely unaccountable unless we 

 conceive the fact that there are considerable 

 variations in the amount of vapour present in their 

 atmospheres. Unfortunately, the photographs of 

 the spectra of these bodies do not include the 

 red region. Sir William Huggins kindly writes, 

 quoting from Vogel's paper in the " Astrophysical 

 Journal" for March and April, 1S95, s0 f ar as 

 Jupiter's satellites are concerned : " From my early 

 observations the lines in the red seen in the 

 spectrum of Jupiter were also probably present in 

 the spectra of the satellites ; so far no observations 

 appear to have been made elsewhere on the 

 subject." It is, however, to be hoped that the 

 observations lacking may be soon made with some 

 oi the modern mighty light-grasping telescopes. 



60, Lttithall Rotul, Da'.slon, N,E. 



WHERE AMBER IS FOUND. 

 By R. Dickson-Bryson, B.A., F.P.S., F.K.As.S. 



A IfBER is chiefly brought from the Baltic. 

 The prolific centre is the peninsula of 

 Samland in Eastern Prussia There amber mining 

 is carried on to a large extent. Ingenious con- 

 trivances for sifting the precious mineral thrown 

 up by the sea are also employed. These ejections 

 occur regularly duri:i« the November and December 

 norm ' ,ries amber pro' 



•vhat geological epoch it belonged, and how 

 it came to be engulfed in the Baltic, were 

 problems that long baffled research. 



Amber is generally supposed to be a marine 



produ'.' lit in huge radial masses at the 



he Baltic This was It Berendt's 



Me advanced the theory thai at a time 



when my was ( :h I lie 



ea, (he amber I 

 upon islands situated north of the prevent 



^cumulated and 

 was ultim U 



It is to Professor Zaddach, of Konigsberg, we 

 owe almost all the knowledge of the subject we 

 possess. He explored the strand hills of Samland, 

 and discovered three systems or groups of layers : 

 the upper one being of diluvial marl and sand, 

 the middle one a bed of lignite, and the lowest 

 one a layer of greensand. All Ihe strata 

 contain amber, the upper one in isolated pieces, 

 while the greensand contains a stratum four 

 or five feet thick of very dark earth, called " blue 

 earth," in which amber occurs so plentifully 

 that an area of fifty or sixty square rods .nil. 

 thousand pi Unds "I the precious mineral. 

 . the great amber mine of the world, and the 



only place when.- the geological conditions admit 

 eons study. It is nowhere else 

 in Its primary plat e ol depi 1 > 

 Zad ' bowed that tin: " blue 



earth" stratum, which in many places sinks to 



be miner's shafts, also 1 mis 



N 2 



