;o2 



NA TURE 



[January 24, 189; 



tioaity of ihe phenomeoa for so long a time seems to confirm the 

 idea of a variety of periods for the particles, and indicate also 

 the repeated omission of the meteors from the body of the 

 comet. If the forces of disruption were only those which have 

 ordinarily been considered, the meteirs would be dispersed in a 

 long thin stream along the length of the orbit, as in the case 

 of the November meteors ; but since Ihe orbits of the meteors 

 are variously inclined lo that of the comet, another force, acting 

 transversely to the plane of the orbit, must be admitted as an 

 important factor. The anomalous phenomena of the tails of 

 some comet-i — a subject with which Dr. Bredichin is already 

 closely associa'ed-and the energetic emis-ions which have been 

 noted in several comets, includmt; that which is connected with 

 the Perseids, serve to demonstrate the possibility of such an 

 action as that which he supposes to have taken place in the case 

 of this swarm. 



Comet 189+ I (Denning) and Brorsen's Co.met.— Dr. 

 Hind cmlributes to Ihe current number of the Aslronomische 

 XaehrichUn (No. 3271) a very inieroting note as to the identity 

 of Denning's comet with that discoveied by Brorsen. To 

 investigate the question, he has found, with M. Schulhof's 

 elements for Denning's comet and Dr. Lamp's elements for 

 Brorsen's comet, that the distance of the orbits would be 

 00367 in Longitude 285' (1894 'o), and that in April 18S1 the 

 comets approached one another within a distance of 0.1 38. 

 On Ibis account, he says, during Ihe comet's recession from 

 perihelion, might rot Brorsen's comet have met with a cata- 

 strophe, causing disintegration and the return of a portion of it 

 to perihelion, in a somewhat different orbit, in Denning's comet 

 of last year ? 



Dr. E. Lamp has also considered this question of identity, 

 and, in referring lo Dr. Hind's note, writes that the similarity 

 of the two orbits is very striking, and that, in the beginning of 

 1881, the two bodies must have been very close lo one another 

 near the point of intersec'ion of the two orbits. With the same 

 elements as used by Dr. Hind, he finds the point of intersection 

 of the orbits in Longitude 28+ 47' and South Latitude t 57'. 

 The places of the two bodies are then as follows : — ^ 



True anomaly 

 Ecc. anomaly 

 Radius vector 



Oenntog. 



154 21 

 123 22 

 5-240 



169 7 

 147 25 



5'2i8 



The point of nearest approach in the orbit of Denning's comet 

 occurs ill a position 5' behind, and in Ihe Brorsen's orbit 4' 

 before, the aclual place, the distance between these points being 

 o°022 radii of the earth's orbit. Dr. Lamp suggests that, by 

 decreasing Scliulhol's value of the mean daily motion by about 

 28', the comets would Ihus be brought together. The question, 

 however, is in a very undecided state, but .astronomers will await 

 with interest the results of Dr. Lamp's investigation as to whether 

 the comets furnish an instance of a mere approach or of a real 

 physical connection. 



Stars having Peculiar Spectra. — Prof. E. C. Picker- 

 ing slates in the Aitronomisc/ie Nachrichttn, No. 3269, that an 

 examination of photographs of stellar spectra, taken at the 

 Arequipa Station of the Harvard College Observatory, has led 

 lo Ihe discovery of four new variable stars in Centaurus, 

 Lupus, Pavo, and Microscopium, and ten other objects with 

 spectroscopic peculiarities. Of these, the spectra of five are 

 classified as Type IV. ; two appear lo belong lo Type V. ; one 

 (K.A. l8h. 384m. Decl. - 27 55') is a nebula; one h.as H" 

 bright ; and the photographic spectrum of the remaining object 

 contains no blue light. To shuw how ililficult it is lo draw 

 any sharp distinction between nebulx and bright line stars, we 

 quote the concluding paragraph of Prof. Pickering's communi- 

 cation. "The photographic spectra of laint gaseous nebula: 

 and stars of the fillh Ijpe closely roemblc each other, and can 

 only be Hislinguishcd by Ihe wavelength of Ihe principal 

 blight line. In ga'cous ncbulic this line (5007) is of greater 

 wave-length than Wa, while in sl.irs of llic hlih type, the line 

 4688 is of dhorler wavelength. A superposition of a chart 

 and spectrum plate of the star whose apprommalc position (or 

 1900 it R.A. = lsh. torn. Decl. -45' 17', which has b;en 

 announced ai a star of the fifth type (Astronoinische Nach- 

 ridilcn, vol. 135, p. 195), shows ihat this object is in reality a 

 gaieoiLi nebula." 



NO. 13 I 7, VOL. 51] 



NITROGEN FIXATION IN ALGyE. 



I TN Nature of March 29, 1S94, Prof. Marshall Ward gave 

 a clear and excellent n'siimi.' of cerLtin aspects of the ques- 

 tion of nitrogen fixation in plants. Since the publication of 

 that article, fresh and most important additions have been 

 made 10 the subject. 



Last May, P. Kossowilsch published an account of bis experi- 

 ments on .^Klgie in respect lo their nitrogen-fixing powers {Bot. 

 Zcilutis, May 16, 1S94), and a short account of this contri- 

 bution should form an appropriate supplement to Prof. Ward's 

 paper. 



Ill 18SS, Prof. Frank, of Berlin, had stated his opinion that 

 Alga: possessed the power of free nitrogen fixation. 



In 1892, Messrs. Schloesing and Laurent published an account 

 of their classical researches dealing with many plants, among 

 which Algae also found a place. Their experiments with these 

 forms range in two series. In the first they found that if they 

 kept soil, covered with .Vlgce and containing bacteria of certain 

 kiuds, under observation for some time, an inciease in nitrogen 

 was perceptible. .On the other hand, if they prevented the for- 

 mation of .'Vlga;, although the same bacteria remained, there 

 was no noticeable addition to the nitrogen of the system. In 

 the second set of experiments, in which different Algx were 

 employed, no nitrogen fixation could be perceived. It was 

 evident from this that either particular kinds of Alga; only have 

 "fixing " powers, or that suitable bacteria were not simul- 

 taneously present in the second case, and that .\lgcc can only 

 fix with the additional aid of these micro-organisms. 



In Ihe following year, Koch and Kossowitsch devoted 

 their attention to the subject, and went over much the same 

 ground as Laurent and Schloesing, confirming iheir results, 

 and adding ne«' facts, the value of which, h iwever, was some- 

 what enhanced by the algal cultures never consisting of any 

 single species alone, but of several intermingled. Accordingly 

 when, in 1894, Kossowitsch set himself the task of determining 

 whether Alg;x; in themselves possess the power of assimil.iting 

 free atmospheric nitrogen or not, the first obsl.icle he had to 

 overcome was the difficulty of finding a method by which he 

 could obtain a single algal species in absolute puiity. This 

 was ultimately effected by growing the Algx on gelatinous 

 silicic acid permeated with a nutritive solution, and subse- 

 quently on sterilised sand also containing food solution. The 

 steps by which the isolation was effected were slow and beset 

 with difficulties, which sprang up in the most unexpected 

 manner, and the pages of Kossowitsch's memoir which deal 

 with this subject possess a separate and great interest of Iheir 

 own ; space, however, will not permit that the matter be 

 detailed here. Having obtained the Alg.x in a state of purity, 

 the next step was to transfer them to the apparatus in which 

 their nitrogen-fixing powers were to be lesteil. 



'Ihis consisted of a central air-tight vesstl connected with a 

 series of U-tubes, which were blown into bulbs at certain inter- 

 vals. These bulbs contained strong sulphuric acid. The whole 

 apparatus was sterilised, and the Algx under consideration 

 sown upon a sterilised nutritive substratum in the central vessel. 

 Air freed from all traces of nitrogen compounds was blown into 

 the vessel through the U-lul)es, the sulphuric acid in which 

 killed any organisms which might be contained in this air. 



The Alga which was first experimented on was Cyslococcus 

 (or an extremely similar form). Every precaution was taken in 

 introducing this into the apparatus. 



Using a nutritive solution perfectly free from all nitrates, it 

 was seen that the Alga: refused lo show any signs of growth ; 

 it was clear, therefoie, that at le.ast to start development a trace 

 of nitrate must be added 10 the saml. The .addition of other 

 nitrogen compounds was found to be useless, and accordingly a 

 small and accurately measured quantity of a nitrate was mixed 

 with Ihe food solution in the central vessel. The whole ap- 

 paratus Ihus fixeil up was placed in the light, and left for some 

 weeks. At first rapid increase in ihe Algie was noticeable, 

 but after ihe lapse of about three weeks things evidently came 

 to a standstill. 



The oddiiion of more nitralcfree nutritive solution gave 

 no result ; but if only the merest trace of a nitrate were 

 added, iheic was an immediale resumption of activity. 



These facts in themselves are very good proof of the inability 

 of Cyslococcus to fix atmospheric nitrogen ; but to make mailers 

 doubly sure, a careful chemical analysis was made. This showed 



