280 



KNOWLEDGE. 



[Dkcember 1, 1896. 



and ]\[aginus, of the October plate, are seen in tliis- the 

 first, partly; the seconcl, wholly, lleinsius, to the oast of 

 Tycho, is very easily identified from the remarkable way in 

 which throe great parasite ring plains have invaded and 

 destroyed its southern wall. On the opposite side of Tycho 

 is Pictet, a walled plain as irregular as Heinsius is regular ; 

 beyond it, the regular ringed plain, Saussure. West of 

 Saussure, the photograph shows beautifully a mountain 

 range which makes on this side, as it were, a second ram- 

 part to the plain. Three ringed plains follow to the north. 

 In the last of these. Miller, the central mountain, which 

 almost exactly marks the prime meridian of the moon, 

 still just rises above the shadow of the eastern wall. 

 Further north is Walter, the largest walled plain of the 

 district, one hundred miles in diameter. The region to 

 the east contains several very regular objects : Lexell, a 

 regular walled plain ; lialland Hell, two ringed plains with 

 five central mountains, well shown in the photograph. 

 Walter, Lexell, Ball, and Eegiomontanus, the latter an 

 irregular walled plain on the edge of the photograph, border 

 a considerable area less broken than most of this district. 

 In this more open country Hell is the principal formation. 



East of Hell is I'itatus, a great walled plain, which, 

 with its companion Hesiodus, end in this direction the 

 highlands of Tycho. Beyond them, to the north, lies the 

 great grey plain, the Mare Nubium, the waters of which - 

 if, indeed, it ever contained water — seem to have eroded 

 part of the northern wall of Pitatus, and to have lowered 

 that of its companion. 



The terminator is occupied, proceeding from the south 

 to the north, by Licetus, Faraday and Stofler, and Alia- 

 censis, the great wall of which shines out in a fine arch at 

 the foot of the plate. 



♦ 



It has been recently discovered that iodine exists in 

 combination in the human body. It occurs in the thyroid 

 gland, and may be concerned as the essential chemical 

 substance in the internal secretion of the gland. The 

 proof of the occurrence of iodine in the living structures 

 of animals is of great scientific interest and importance, 

 and is the most remarkable discovery made by chemical 

 physiology for some time. 



The annual production of gold from all the various 

 sources is at present about £42,000,000. This is twice 

 the amount produced seven years ago. It is greater than 

 at any previous period in the history of the world, the 

 next greatest annual output being that of the year 1853, 

 when the river gravels of California and Australia were 

 in their most productive state. The amount extracted 

 in the year was then estimated at £'38,000,000. More 

 than half of the total yearly amount is now got by the 



amalgamation process from crushed vein stuff. 

 — ,-•-, — 

 Through the courtesy of Messrs. Beck, we have been 

 able to examine and practically test their new Frena 

 Camera of the memorandum size. This is an excellent 

 little instrument, and is capable of producing good work. 

 It is simple and efi'ective in mechanism, and should prove 

 very useful to amateurs, especially as its price is a popular 

 one. The serrated edges of the celluloid films are a dis- 

 advantage, as on this account a considerable portion of 

 the picture is lost. On the other hand, by this means the 

 process of changing the films is greatly simplified. 



> ^« 



An X-ray tube has lately been brought out by Messrs. 

 Watson with greatly increased distance between the 

 terminal attachments outside, and having also a palladium 

 ring as anode placed above a platinum anticathode, the 



principle of which is that, when warmed, this palladium 

 ring gives up some of its occluded hydrogen. In this way, 

 when the vacuum gets too high it is possible to bring it 

 down again at will. We have had one of these tubes in 

 daily use for the last fortnight, a ton-inch spark coil baing 

 used. The vacuum has not perceptibly altered, and we 

 have not, as yet, had occasion to warm it. It can only 

 be supposed that the palladium ring has given up some 

 hydrogen without warming. The results attained with a 

 screen are particularly good. But in case waruung should 

 be necessary, the tube, as now arranged, would have to be 

 disconnected to carry this out. To avoid this it might be 

 suggested that the ring might be done away with, and 

 instead that a small bulb be attached to the exhaust tube 

 containing a smnll quantity of spongy palladium (which 

 occludes about two hundred times its volume of hydrogen). 

 The vacuum could then be adjusted while the tube was in 

 action. , . , 



Investigations have been made by different observers to 

 determine whether the Koutgen rays are homogeneous or 

 not. The methods employed consisted in testing whether 

 substances placed in the path of the rays exhibited selective 

 absorption, and distinct indications of this were found, 

 showing that R(iatgen rays are not all of one kind, but 

 that the efl'ects are produced by radiations of different 

 wave-length. Dr. Famm, by means of diffraction experi- 

 ments, has found that the greatest wave-length of the 

 Rontgen radiation is about one-fifteenth that of the shortest 

 ultra-violet waves hitherto measured. Herr Arnold finds 

 that the Rontgen rays can be applied to detect adulteration 

 in various articles of food ; the foreign substances added 

 frequently greatly altering the transparency of the article 

 tested, and thus changing the character of the shadow 

 picture thrown on a Huorescent screen. 



In France, where so much has been done by M. Moissan 

 in the way of the production of small artificial diamonds by 

 means of his electric furnace, a recent observer, M. Rossel, 

 has detected the presence of small diamonds in certain 

 specimens of hard steel. By suitable treatment, insoluble 

 fragments were got from the steel which possessed all the 

 properties of natural diamonds. M. Moissan's method of 

 preparing artificial diamonds consists in saturating iron 

 with carbon at a high temperature in the electric furnace, 

 and cooling the fused metal under a high pressure. The 

 carbon present thus assumes the crystalline form of 

 diamond. In M. Rossel's specimens the steel had been 

 subjected to a similar treatment in the course of its manu- 

 facture, and the diamond crystals were produced from the 

 carbon always present in steel and cast-iron. 



The most ancient copper mines in the world are those 

 of the Sinai peninsula, near the Gulf of Suez. M. 

 Berthelot gave an account of them to the French Academy 

 of Sciences in August. They were abandoned about three 

 thousand years ago, after having been worked for some 

 hundreds of years. The process used for the reduction of 

 the ore was similar in principle to that used at the present 

 day. — «-. — 



In the recent researches on light and ethereal vibrations 

 of all sorts, the interesting fact has been discovered that 

 the light emitted by glow-worms is able to penetrate 

 blackened paper, and affects a sensitive photographic plate 

 placed underneath. — -^ — 



Messrs. Newton ct Co. have just issued a new list of 

 some very useful series of lantern slides. Amongst others 

 may be noticed the series on astronomy taken from photo- 

 graphs which have appeared in Knowledce, a series on 

 British birds' nests, and another on the X-ray photography. 



