January 12, 1922] 



NATURE 



43 



These seeds were not studied at the time, but they are 

 now seen to agree excellently with those of Ranun- 

 culus. They are, properly speaking, achenes, about 

 17 mm. long and i mm. broad, with a fairly long 

 moderately curved beak. The general form approaches 

 that of R. pcnnsylvatiicus, but the achene is less 

 robust. The fossil may be known as R. florissantensis 

 n. sp. Ranunculus has a single seed in the achene. 

 It has been definitely determined for R. acris at least 

 that there is only one ovule. Our fossils, however, 

 verv distinctly show two, after the manner of 

 Hydrastis. They were evidently small and dry at 

 maturity, as in Ranunculus, and the most mature 

 ■ones contain only one seed, dark and clearly outlined. 

 It would be worth while to investigate the immature 

 achenes of numerous species of Ranunculus to deter- 

 mine whether any start with two ovules, one aborting, 

 as I have determined to be the case in Malvastrum. 

 Heer has described a very similar Ranunculus seed 

 i(achene) from the Miocene of Oeningen in Baden. 



T. D. A. COCKERELL. 



University of Colorado, Boulder, Colorado, 

 December 8. 



The Absorption of Fluorescing Sodium Vapour. 



According to Bohr's theory concerning the origin of 

 spectral lines, electrons in the atoms of sodium vajwur 

 under the influence of exciting D radiation are dis- 

 placed from their normal 1-58 orbit to the 2/) orbits. 

 During the return of the electrons to their normal 

 orbit the sivcalled "resonance" radiation, first ob- 

 served by Wood (P/ji7. Mag., November, 1905, and 

 "Researches in Physical Optics," part 2, p. 166), is 

 ro-emitted as fluorescent light. It has been suggested, 

 therefore, by more than one observer (Foote and 

 Meggers. Pliys. Rev., vol. 15, part 4, p. 323, and Phil. 

 Mag., vol. 40, p. 80, 1920) that fluorescing sodium vapour 

 should absorb lines of the first and second subordinate 

 series 2p,^,- nis and 2p^.~md . To test this point I have 



made use of the experimental arrangement outlined 

 below. While a negative result was obtained, it 

 seems worth while to record the trial, along with one 

 or two suggestions for a more rigid test which I am 

 not able to make at present. 



A narrow beam of light from a Nernst lamp 



tversed the tube AB, some 25 cm. long, into which 



me sodium had been distilled in high vacuum (Fig. i). 



i^y means of a lens the light was focussed on the slit 



of a Hilger constant-deviation spectroscope. Directly 



below the sodium tube was a sodium-potassium alloy 



*'lamp" CD, a slight modification of the type re- 



NO. 2724, VOL. 109] 



cenUy described by Neuman (Proc. Phys. Soc. London, 

 vol. 33, part 2, February 15, 1921). Both tubes were 

 enclosed in an electric oven, by means of which they 

 could easily be heated to 300° C. or higher. For two 

 reasons it seemed to the writer that this lamp should 

 be most suitable. In the first place, resonance can 

 best be excited by very narrow spectral sources, and 

 it had been shown that the light from the lamp con- 

 sisted almost entirely of D lines of narrow width. 

 .\gain, it could be operated at temperatures at which 

 resonance is obtained in sodium vapour, so that it 

 was ix>ssible to place the two tubes side by side in 

 the same oven. 



At temjxratures ranging from 200° C. to 300° C, 

 therefore, observations were made to see if there was 

 any difference in the absorption spectrum when the 

 exciting lamp was "on " and "off." The D absorp- 

 tion lines were easily visible, but not the slightest 

 difference could be detected in the two cases. It is 

 ix)ssible, however, that with an improved arrange- 

 ment the absorption looked for might occur. The 

 lines of the subordinate series most likely to be ab- 

 sorbed are the first members, which, however, are 

 in the infra-red region and could not be observed 

 visually. A much better test, therefore, would consist 

 in photographing with dicyanine-stained plates in the 

 hope of observing absorption of the doublet A 8195 and 

 18184. Again, the intensity of the exciting light may 

 not have been great enough to put a sufficiently 

 lariie number of atoms in the desired state. This 

 Hifticulty would be lessened by the use of two or 

 three lamps, or possibly by adapting for use with 

 stadium some such arrangement as was used by Fiicht- 

 bauer (Phvs. Zeit., vol. 21, November i and i;. 11)20"^ 

 for observing resonance in mercury vapour. Finally, 

 a longer absorption tube obviously would be more 

 desirable. With improvements such as are suggested 

 a much more rigid test could be made. 



John K. Robertson. 



Queen's University, Kingston, Canada, 

 December 17. 



The Message of Science. 



Mr. \\'. Robertson's letter in Nature of Januarys 

 is verv timelv. Mav I invite him and those his letter 

 has interested or impressed to put into practice, in 

 Middlesbrough or any other town, the "most prac- 

 tical suggestion of immediate value " he describes, 

 with one important addition. Some of us have 

 recently been striving to get his suggestion, thus 

 widened and clinched, made operative in other British 

 centres of population on behalf of the British Science 

 Guild, the objective of which comprehends the exact 

 dutv Mr. Robertson acclaims and the methods of 

 which in a new campaign have been dictated by a 

 livelv sense of provincial and metropolitan needs in 

 the harnessing of science to important public tasks. 



Our methods begin iust where those of so many 

 other people leave off. We ask local scientific 

 societies and organisations and all who desire to 

 make their special scientific equipment of use to their 

 times to establish touch at once with the important 

 local organisations and groups in which business 

 men, administrators, and the occupational classes 

 gather, and with them to consider " the progressive 

 connecting of science with individual and corporate 

 conduct." not in general, nor on another continent, 

 but in their own towns (where facts can be known 

 and methods tested), and in anv of the problems on 

 which much public time and public monev have in- 

 evitablv to be soent. That suffices for a beginning. 



Many are feeling to-dav that science should become, 

 and can become, the "chief formative factor of modern 



