ULY 



890] 



NATURE 



23'5 



Among the papers read at the closing meeting of the 

 Royal Society, was one by Prof. Ewing, of the Duudee 

 College, entitled, "Contributions to the Moiecular Theory of 

 Induced Magnetism," in which experiments of a novel and 

 curious kind were described, leading to an important conclusion. 

 Prof. Ewing has examined experimentally Weber's theory of 

 molecular magnets, according to which the molecules of iron 

 are always magnets, which point anyhow in an unmagnetized 

 piece, but are turned round to point one way when the iron is 

 magnetized. It is well known that in the development of this 

 theory by M axwell and others there has been much difficulty in 

 reconciling the results of the theory with what is known about 

 the magnetic quality of iron and steel, and many arbitrary 

 assumptions have been suggested in order to make the theory 

 fit the facts. Prof. Ewing's experiments have removed this 

 difficulty, showing that no arbitrary assumptions are necessary, 

 and that the known character of the magnetizing process may 

 be deduced from the molecular theory in its simplest form. 

 The experiments were made by means of a model in which a 

 large number of small pivoted permanent magnets are grouped 

 to represent the molecular structure of iron. When a magnetic 

 field is applied, the action of the small magnets on one another 

 makes them behave in a way that exactly agrees with the 

 observed behaviour of a bar of solid iron when it is magnetized. 

 The model exhibits all the variations of susceptibility which are 

 known to take place, and explains how magnetic hysteresis 

 occurs without anything like friction among the molecules. 



According to the Ceylon Observer, Mr. A. T. W. Marambe, 

 of Kandy, the translator of "Gulliver's Travels" and the author of 

 " A Practical Synopsis of Ceylon History," has in preparation 

 a little work on the Veddah language. Many have attempted 

 this task before, but without success. Besides Veddah songs, a 

 description of habits and customs, &c., the book will have a 

 completer list of words than has hitherto appeared. 



An exceptionally pretty and instructive series of new experi- 

 ments, upon the action of carbon heated to whiteness in the 

 electric arc on various gaseous compounds, are described in the 

 current number of the Berichte by Prof. Lepsius, of Frankfurt. 

 Perhaps the most important are a group of four experiments 

 Uiustrating the relative combining powers of the four elements 

 iodine, sulphur, phosphorus, and carbon. The apparatus em- 

 ployed consists of a specially modified Hofmann eudiometer, one 

 limb of which is 40 mm. in diameter and 300 mm. long, and the 

 other longer limb narrower and furnished with a mercury reser- 

 voir at its upper end. The wider limb, which is the reaction- 

 tube, is furnished with a stop-cock at the top, and just below 

 this are two tubuli through which the adjustable carbon poles are 

 inserted. At the base of the wider limb a second stop-cock is 

 placed so as to permit of the adjustment of the mercury. The 

 gas to be experimented upon is introduced into the apparatus at 

 the upper stop-cock by allowing mercury to run out at the base. 

 Four such eudiometers are arranged in a row, and lOO c.c. of 

 gas introduced into each. Into the first, hydriodic acid is intro- 

 duced ; into the second, sulphuretted hydrogen ; into the third, 

 phosphuretted hydrogen ; and into the fourth, marsh-gas. The 

 gases thus stand at the same level in each of the four reaction- 

 tubes. The current from a battery whose electromotive force 

 should amount to 60-80 volts is then allowed to pass between 

 the carbon poles, which are, of course, in contact at first, and 

 then gradually drawn away until the maximum arc is obtained. 

 Each reaction may be performed separately, or all four may be 

 allowed to proceed simultaneously by adopting an arrangement 

 in multiple arc. In hydriodic acid the brilliant arc light is 

 tinted a magnificent purple and the whole space above the 

 mercury becomes filled with violet vapour of iodine. Notwith- 

 standing the considerable heating effect of the discharge, the 

 volume of gas perceptibly diminishes, the liberated iodine 

 NO. 1079, VOL. 42] 



rapidly depositing in minute crystals upon the walls of 

 the tube. So rapid, indeed, is the diminution in volume, 

 that mercury requires to be poured into the reservoir to 

 prevent the entrance of air into the reaction-tube. In a very 

 few minutes the reaction is complete, and the mercury ceases to 

 rise. In sulphuretted hydrogen the light is coloured blue, and 

 copious clouds of sulphur are produced, which settle upon the 

 walls in the form of a white transparent coating. The volume 

 of gas is considerably augmented, owing to the expansion by 

 heat, and the reaction is likewise completed in a very brief 

 space of time. In phosphuretted hydrogen the arc glows with a 

 dazzling red light ; the volume visibly augments at a rapid rate, 

 and red clouds of phosphorus are thrown off, the glass walls 

 being covered with red phosphorus, among which are to be 

 found notable quantities of the ordinary yellow variety. The 

 mercury attains its maximum height in the narrow limb in a 

 minute at most from the moment of switching on the current. 

 In the case of marsh-gas, the whiteness of the arc appears at first 

 to be rendered more intense, and is surrounded by dense black 

 clouds of carbon, which form a striking background. The upper 

 part of the vessel, however, soon becomes covered with an opaque 

 deposit, which perceptibly diminishes the brilliancy of the light. 

 The volume appears to increase by leaps and bounds, and in a 

 few seconds attains its maximum. At the end of the experi- 

 ment, after cooling, the volume of hydrogen left in the first 

 case is 50 c.c, in the second 100 cc, in the third 150C.C., and 

 in the fourth case 200 c.c, thus showing in a most striking 

 manner that an atom of iodine combines with one atom of 

 hydrogen, sulphur with two, phosphorus with three, and carbon 

 with four atoms of hydrogen. 



The additions to the Zoological Society's Gardens during 

 the past week include a Bosman's Potto {PerodicHcus potto) from 

 West Africa, presented by Mr. P. S. S. Radcliffe ; a Harnessed 



Antelope ( Tragelaphus scriptus cJ ), a Antelope ( Cervicapra 



sp. in. c5 ), two Marabou Storks {Leptoptilus crumewferus) from 

 Gambia, West Africa, presented by Dr. Percy Kendall ; an English 

 Wild Bull {Bos iaurus, var.) from Chartley, Staffordshire, pre- 

 sented by the Earl Ferrers ; a Ring-tailed Coati {Nasua rufa 9 ) 

 from Buenos Ayres, presented by Mr. C. W. Blacklock ; two 

 Tigers {Felis tigris 6 ?)from India, presented by H.R.H. the 

 Duke of Clarence and Avondale ; a Wedge-tailed Eagle {Aquila 

 audax) from Australia, presented by Captain Salvin ; an Alligator 

 {Alligator mississippiensis) from the Mississippi, presented by 

 Mr. Alexander Finlay ; two Nightingales {Daulias luscinia), 

 British, presented by Mr. J. Young, F.Z.S. 



OUR ASTRONOMICAL COLUMN. 



Objects for the Spectroscope. 



Sidereal Time at Greenwich at 10 p.m. on July 3 



i6h. 47m. 29s. 



j Mag. 



(i)G.C. 4373 



(2) 387 Birm. 



(3) rr Herculis 



(4) € Herculis 



(5) 202 Scbj. ... 

 (6> V Boatis ... 



56 



3 

 3 "4 



8 

 Var. 



Greenish-blue. 



Reddish-yellow. 



Yellow. 



Bluish-white. 



Very red. 



Reddish-yellow. 



Decl. 1890. 



+ 6637 

 + 847 

 +3656 

 +31 5 

 -19 24 

 +39 21 



Remarks. 

 (i) This is the planetary nebula famous in the history of 

 astronomy as the first nebula which was examined by the spec- 

 troscope. The nebula, though small, is remarkably bright, 

 and the lines in its spectrum are at least as bright as those in 

 the nebula of Orion. The three principal lines in the green, 

 and the hydrogen line at G, are seen without any difficulty. 



