Nov. 24, 1887] 



NATURE 



79 



drawn to the difference in expression employed by Proclus, viz. 

 that Euclid arranged many works of Eudoxus, and completed 

 many of those of Theoetetus, from which Dr. Allman infers 

 that, " whereas the bulk of the fifth and twelfth books is due to 

 Eudoxus ; on the other hand, Thecetetus laid the foundation 

 only of the doctrine of inc Miimensurables as treated in the 

 tenth book. In like manner from (/) we infer that the thir- 

 teenth book, treating of the regular solids, is based on the 

 theorems discovered by Thea^tetus ; but it contains, probably, 

 a recapitulation, at least partial, of the work of Aristseus" 

 [cf. Nature, ubi stipra\. 



The author, in conclusion, draws the inference that the prin- 

 cipal part of the original work of Euclid himself is to be 

 found in the tenth book. " De Morgan suspected that in this 

 book some definite object was sought, and suggested that the 

 classification of incommensurable quantities contained in it was 

 undertaken in the hope of determining thereby the ratio of 

 the circumference of the circle to its diameter, and thus 

 solving the vexed question of its quadrature. It is more 

 probable, however, that the o!)ject proposed concerned rather 

 the subject of Book xiii., and had reference to the deter- 

 mination of the ratios between the edges of the regular solids 

 and the radius of the circumscribed sphere, ratios which in all 

 cases are irrational. In this way is seen, on the one hand, the 

 connection which exists between the two parts of the work of 

 Thea^tetus, and, on the other, light is thrown on the tradition 

 handed down by Proclus, that Euclid proposed to himself the 

 construction of the so-called Platonic bodies as the final axiom 

 of his systematization of the ' Elements.'" Here for the pre- 

 sent I take leave of the author. I have read his several parts 

 as they have appeared with very great interest, and have en- 

 deavoured, without going far into technical details, to indicate 

 the results arrived at, and I hope that some will have been induced 

 to go to the fountain-head for undiluted draughts from this refresh- 

 ing stream. I need only repeat the expression of the wisk, 

 more than once previously uttered, that the several papers may 

 be collected into a handy volume, in which case they will fitly go 

 side by i-ide with the works of Bretschneider, Cantor, Tannery, 

 and other distinguished labourers in the same field. R. T. 



The Chromosphere. 



Having lately devised a spectroscope with two small sextant 

 telescopes and two small prisms, one of "extra dense " glass by 

 Hilger, I attached it to a2i-inch telescope, and tried its powers 

 on the sun on the 6th inst., with the result that not only were 

 the rays C and D* easily visible as bright lines, but I also found 

 that by opening the slit and keeping the brighter part of the 

 spectrum out of view I could see the actual ragged surface of the 

 *' itorm-tossed sea of hydrogen." 



I found the depth of the chromosphere to be about 10", by 

 estimating the length of the bright line when exactly tangential 

 to the limb. 



This result shows what is possible with small instrumental 

 means, though probably much was due to an exceptionally clear 

 sky. ■ John Evershed, Jun. 



Perception of Colour. 



In answer to Mr. T. W. Backhouse, I would suggest that he 

 should use the spectroscope in the following manner. Hold it 

 between the luminous object (moon or street lamp) and the eye 

 at a distance of about 12 or 15 inches from the latter, so 

 that only part of the spectrum is seen. Then remove the 

 specti'oscope sideways, and pass it quickly through its old 

 position. A flash of coloured light will be seen, and no matter 

 what may be the direction of the spectrum with reference to the 

 line of motion the flash will always be seen to travel from the 

 red end towards the blue end. Each part of the spectrum can 

 be examined separately. 



Whether this phenomenon is due to a later perception or 

 longer retention of the blue light as compared with the red I 

 cannot at present say, but I think it is independent of the 

 inten^ties. C. E. Stromeyer. 



Swifts. 



On June 19, and again on June 21 last, in the evening, I 

 watched avast concourse of swifts flying over this town. They 

 slowly soared upward-, shrieking and striking at each other, and 

 at last went so far up in the sky as to look like a cloud of black 



gnats. I watched them till dusk, when their faint cries were 

 still audible, and when these had died away in the distance I 

 waited long for the birds to descend, but they did not, probably 

 because they were old birds which had been sitting all day, and 

 were glad of an opportunity to stretch their long wings in a few 

 hours' flight. No great height would necessarily be attained by 

 the birds during the short midsummer nights. I noticed on 

 several subsequent evenings that at least some of the swifts of 

 the town did not stay up till dusk ; but I am not the less 

 positive that on June 19 and 21 they spent the night in the sky. 

 Stroud. C. B. WiTCHELL. 



Note on a Madras Micrococcus. 



The sole charge of a Presidential Museum and the study of 

 that high-road to pathological eminence, bacteriology, are un- 

 fortunately not compatible, but I have not been able to resist 

 the rough investigation of a phenomenon wh'ch stands pro- 

 minently out before my eyes as I write. It consists of a thin, 

 homogeneous, pale pink pellicle, covering the chunam (shell- 

 lime) walls of my house on the side exposed to the heavy 

 monsDon rain, which is at present varying the monotony of 

 our "fine sunny days," which so impress our energetic cold- 

 weather visitors, who learn all about India from Calcutta to 

 Cape Comorin in a three weeks' tour. So evenly is the pink- 

 coloured material distributed in my library, that its walls look 

 as if they had been painted on one side, and whitewashed on 

 the other three sides. This coloration, which is well known 

 in Madras, is, I believe, commonly attributed to some occult 

 chemical action on the lime, but a cover-glass specimen stained 

 with methylene blue, and examined with a |-inch objective, 

 decides at a glance that it is caused by a Micrococcus, which, in 

 its microscopical appearance, presents nothing remarkable. 



The mode of growth of this organism on or in artificial 

 nutrient media I have not attempted to investigate, but I notice 

 that white lead does not agree with it, as its growth ceasei 

 abruptly at the painted framework of the doors and windows. 



As I cannot find any description, in the reference-books at my 

 disposal, of a Micrococcus which corresponds to the one here 

 described, I christen it provisionally Micrococcus madraspatanus, 

 Madraspatan being the old name of Madras, which is, according 

 to Lassen, a corruption of Manda-rajya, meaning " realm of 

 the stupid."' Edgar Thurston. 



Government Central Museum, Madras, 

 October 26. 



Catharinea undulata. 



In October 1886 I found, in Hertfordshire, two specimens of 

 Catharinea undulata, Web. et Mohr., bearing fruit in the axils 

 of the leaves ; those specimens I unfortunately lost. 



When this summer in Norway, I had the good fortune 

 and pleasure of meeting Prof. S. O. Lindberg, of Helsingfors, 

 and I mentioned the fact of the discovery to him. He then told 

 nie that similar specimens had been found in Norway some 

 little time before, and described under the name of C. anomola, 

 Lindberg and Bryhn. In consequence of my conversation with 

 Prof. Lindberg I looked again this autumn for specimens similar 

 to those I had found last year, and after some little search I 

 f.und some half-dozen or so near the same spot where I had 

 found them last year. 



The specimens I now have in my possession bear fruit at the 

 apex of the stem, and also one, or sometimes two, setae in axils 

 of leaves below the apex. These pleurocarpous setae differ from 

 the acrocarpous by being twisted in a spiral manner, not being 

 straight as the acrocarpous fruits are ; they are inserted in a 

 vaginula in the axil of the leaf, without any perichoetial leaves. 



I thould be glad if bryologists generally would look out for 

 specimens of this form. I should also consider it a great favour 

 if any collectors who may find specimens would let me know, 

 and provide me with an accurate description, or send me the 

 specimens for inspection. Specimens should be preserved in 

 strong methylated spirit, otherwise it may be difficult to verify 

 some important details. 



There is a brief reference to the Norwegian specmiens m llie 

 Botanische Centralblatt, Band xxix. p. 2, 1887; the full de- 

 scription is, I believe, to be found in the Botaniska Notiser, 

 1886, p. 157 ; the latter I have not yet been able to obtain access 

 to, though I hope to do so soon. J. Reynolds Vaizey. 



Botanical I aboratory, Cambridge, November 18. 



