i8o 



NA TURE 



[December 23, 1897 



Again, in Astr. Nach., 3463, he gives notice of two new 

 variables — probably of short period — B.D. + 67°'i 124 in Draco, 

 and B.D. + 30° '1329 in Gemini, with respective positions: 

 R.A. iQh. 9m. 54s., Decl. + bf 2' -4, and R.A. 6h. 37m. 50s., 

 Decl. + 30° 25'. 



All the positions are given for the epoch 1855. 



Variations in the Spectrum of Nebula in Orion. — 

 Often has severe criticism put scientific facts on a firm.er basis, 

 and such might be said to be the case with Dr. Scheiner's 

 ■doubts concerning Prof. Campbell's observed variations in the 

 spectrum of different regions in the Orion nebula, made in 

 1893. To test the accuracy of some specific observations. 

 Prof. Campbell has called in the assistance of three of his 

 colleagues (Prof. Schaeberle amongst them), and, with the aid 

 of the 36-inch refractor and an efficient spectroscope, different 

 regions of the nebula have been examined to observe the be- 

 haviour of the three principal nebular lines. 



The mode of making the observations was to use a coarse 

 micrometer wire, occulting each of the lines in turn, so as to 

 determine the relative brightness of the remaining two, when 

 all three are observable. 



The following are the results, which in the main all the 

 observers are agreed upon : — Central part of nebula (Trapezium 

 region) : the three nebular lines all conspicuous, the line A. 5007 

 being the brightest, whilst the lines A 4959 and A 4861 are nearly 

 of the same intensity as each other. 



In the region surrounding the star Bond, No. 734, the line 

 \ 4861 was the only one visible, the other two lines having 

 disappeared ; whilst in the region south-west of the Trapezium 

 all three are visible, but the line A 4861 is still the brightest. 



No doubt photographs will be secured whilst Orion is well 

 situated, and so further establish these observations made 

 visually. 



Winnecke's Periodic Comet. — One is reminded on read- 

 ing the life-work of the late Dr. Winnecke, in the last number 

 of Nature, that had he lived a few weeks longer he would 

 probably have seen another return of the periodic comet which 

 bears his name, for it is due at perihelion on March 20, 1898, 

 but of course will be better situated for observation some time 

 before this. The elements and ephemeris as given by Mr. C. 

 Hiliebrand in Astr. Nach., 3447, are as follows : — 



Elements. 



26 October. 1897. 



M = 325 24 267 

 IT = 274 14 33*3 

 n = 100 S3 34-3 

 i = 16 59 34'4 

 1>= 45 37 35'6 



y. = 608-3483 



15 March, 1S98. 



359 3 52 o 



274 14 39-0 



100 53 11-5 



16 59 33 '8 



45 37 147 



608-5559 



1900 



Ephemeris. 

 Decl. log r. 



log A. 



I : >-2ji2. 



1897-98. R.A. 



h. m. s. o / 

 Dec. 21 ... 14 38 14 ... - I 6-6 ... 0-19028 ... 0-28225 ...0-113 



25 ... 51 6... 2 2-3... 17921... 26885... 127 



29 ... 15 428.. 258-6... 16788... 25550... 142 

 Jan. 2... 1824... 3 553 ■■■ 15629... 24228... 160 



6... 32 53-- 4 52-3- 14446 •.- 22929... 179 

 10 .,. 1547 58 ... 5 49'3- 13242... 21659... 200 

 14 ... 16 340... 646-1... 12016 ... 20432... 224 

 18... 20 o... 7421... 10773.. 19259 •• 251 

 22... 3659... 837-0... 09518... 18151 ... 280 



26 .. 16 54 36 ... 9303... 08256... 17122... 311 



30 ... 17 12 49 ... 10 21-3... 06993... 16184... 344 

 Feb. 3 ... 17 31 41 ... -II 9-0. ..0-05738. ..0-15349. ..0-379 



The best time for iriaking a search will be early in the morning, 

 shortly before sunrise, from about now till early in February. 

 The comet is never visible to the naked eye, and will at first be 

 faint with the aid of a telescope ; its apparent path is in a south- 

 easterly , direction through Virgo, Libra, Scorpio, Sagittarius, 

 and Capricorn. 



KEKULE MEMORIAL LECTURE. 

 T an extra meeting of the Chemical Society, held on Wed- 

 ^j,nesday, December 15, Prof. F. R. japp, F.R.S., delivered 

 a memorial lecture in honour of the eminent German chemist, 

 Friedrich August Kekule, whose death occurred in July 1896. The 

 lecturer said that Kekule's supreme merit lay in his contributions 



NO. 1469, VOL. 57] 



A 



to theoretical chemistry. His greatest achievements in this de- 

 partment were the doctrine of the linking of atoms in terms of 

 their valency, and, growing out of this, the theory of the struc- 

 ture of organic molecules, both in open-chain and in closed-chain 

 compounds. These were not recondite theories, hidden away in 

 the depths of the science ; they were organic chemistry itself, 

 and were learnt by students on their first introduction to the 

 subject. Kekul^ acknowledged that his theories were based on 

 Gerhardt's type theory, on Williamson's theory of polyvalent 

 compound radicles and multiple types, and on Odling's theory 

 of mixed types, which was a deduction from Williamson's theory. 

 Less consciously, perhaps, his opinions were influenced by 

 E. Frankland's theory of the valency of elementary atoms, and 

 by Kolbe's speculations on the constitution of organic com- 

 pounds. Kekule developed these ideas, which he found scat- 

 tered throughout the writings of his predecessors, added to them, 

 and welded the whole into the coherent system which formed 

 our present theory of the structure of organic compounds. In 

 Kekule's model of the carbon atom " the four units of affinity," 

 to quote his own words, ' ' radiate from the sphere representing 

 the atom so that they end in the faces of a tetrahedron." This 

 model was destined to play an important part in the develop- 

 ment of theoretical chemistry ; it was the foundation of stereo- 

 chemistry. Kekule's benzene theory was the crowning achieve- 

 ment, in his hands, of the doctrine of the linking of atoms ; it 

 was the most brilliant piece of scientific prediction to be found 

 in the entire range of organic chemistry. What Kekule wrote 

 in 1865 had since been verified in every essential particular. 

 Not only had the various substitution derivatives been discovered 

 in the number and with the properties required by the theory, 

 but various observations which appeared to contradict this theory 

 had been proved erroneous. Moreover, the theory had shown 

 itself to be capable of boundless development, and there seemed 

 to be no limit to the fruitfulness of Kekule's conception of closed 

 chains or cycloids. The extensions of the idea, of which exten- 

 sions Erlenmeyer's naphthalene formula and Dewar's formulae for 

 pyridine and quinoline were among the earliest instances, had 

 gone on increasing in a rapid geometrical ratio, until, at the 

 present day, the literature dealing with cycloids, although of so 

 recent growth, was more than twice as voluminous as that of 

 the paraffinoids. But even in the undeveloped state of the sub- 

 ject prior to Kekule's theory, the facts were apparently so in- 

 intricate and so unconnected that few chemists could claim to 

 have mastered them. The theory appeared ; the previously un- 

 marshalled facts fell into their proper places ; and not only this, 

 but it was possible to say whether, in any given section of the 

 subject, the facts were complete or only fragmentary. The debt 

 which both chemical science and chemical industry owed to 

 Kekule's benzene theory was incalculable. As regards the 

 former, three-fourths of modern organic chemistry was, directly 

 or indirectly, the product of this theory ; and as to the latter, 

 the industries of the coal-tar colours and the artificial therapeutic 

 agents, in their present form and extension, would be inconceiv- 

 able without the inspiration and guidance of Kekule's fertile 

 idea. By the accuracy of his predictions he had done more to 

 inspire a belief in the utility of legitimate hypotheses in 

 chemistry, and had therefore done more for the deductive side 

 of the science than almost any other investigator. His work 

 stood pre eminent as an example of the power of ideas. 



RECENT RESEARCHES ON TERRESTRIAL 

 MAGNETISM} 



II. 



UP to this point we have regarded the system of magnetic 

 forces in play upon the surface of the earth as constant. I 

 have already hinted that this is not the case, and that the difficulties 

 of our investigation are immensely increased by the fact that 

 all the phenomena with which we deal are in a state of flux. 

 Nothing is fixed from year to year, from day to day, from hour 

 to -hour. It is hardly too much to say that at times almost 

 every minute brings with it changes which it is the business of 

 the magnetician to investigate and explain. For the moment, 

 however, I wish to fix attention only upon the secular change to 

 which I have already referred. Not only does the angle which 

 the magnet makes with the geographical meridian vary, but the 

 dip also increases and diminishes in turn. 



1 The " Rede Lecture " delivered in the Senate House, Cambridge, on 

 June 9, by Prof. A. W. Rucker, F.R.S. (Continued from p. 163.) 



