July 17, 1879] 



NATURE 



275 



Figs. 6 to 9 represent several stems and plates isolated 

 in the manner described and magnified 350 times. 



Fig. 6 shows a bent and half tube-shaped stem ; Fig. 7 

 a plate with two apertures; Fig. 8 a plate with alternate 

 and parallel thicker and thinner parts ; Fig. 9 a ramified 

 stem of similar structure. In Fig. 6 the shape of the 

 cross-section is indicated. The alternately thinner and 

 thicker parts in Figs. 8 and 9 correspond to the lamellae 

 of the lime in which they laid imbedded, and therefore 

 probably have their origin from these. 



Now we have only to consider the fibres, which in many 

 parts of the Eozoon, at the borders of the calcareous parts 

 carrying the stems, surround the serpentine-like bands, 

 but which in other parts pass right through the serpen- 

 tine. In Fig. 5 these fibres are marked F, while the 

 serpentine is designated by S. A very well-defined band 

 of fibres is seen in Fig. 10 (magnified 200 times), between 

 the serpentine S and a piece of lime in which obliquely 

 ascending stems are cut right across at the surface of the 

 section, o is a crystal of olivine in course of decomposi- 

 tion, and therefore no longer possessing sharp edges. 



The fibres are imperfectly developed micro-crystals of 

 chrysotile, which like olivine and serpentine consists of 

 silica and magnesia. In many fibre-bands, with the 

 application of strong magnifying powers, it is observed 

 that the fibres are very small four-sided prisms. In Fig. 

 II, near f, such fibres are shown, magnified 500 times ; 

 to the left are long, less distinct, needle-shaped chrysotile 

 crystal*, besides lime (k). 



(To be continued.) 



NOTES . 



Wk have received from the U.S. Si^al Office the monthly 

 Bulletins for November «nd December, 1874, January, 1875, 

 and January, February, and March, 1877. We hope shortly 

 to begin, through the courtesy of General Myer, the regular 

 publication of a map exhibiting the simultaneous monthly means 

 in meteorology of the whole of the Northern Hemisphere. 

 The immense value of such a publication to meteorological 

 science we need not point out, and the enterprise of the U.S. 

 Signal Office in working out and making public these data is 

 beyond praise. 



The Astronomical Museum established by Admiral Mouchez in 

 the Paris Observatory may be considered as now complete. Besides 

 the pictures of the principal celestial objects and portraits of the 

 directors of the Paris Observatory, the hall contains a number of 

 objects connected with astrology as well as astronomy, and a number 

 of historical instruments, as the bar which was used for measuring 

 the Peruvian degree, the similar instrument which was taken to 

 Lapland by the Northern Commission ; the pendulum used by 

 Duperrey, and that used by Fraissinet for measuring the in- 

 tensity of gravity in remote lands, the former being con- 

 structed by Fresnel ; the bi-refracting prism used by Arago for 

 his great optical discoveries, the Dortable meridian circle de- 

 signed by Admiral Mouchez, &c., &c. 



A SOLUTION of a problem which has lately acquired some 

 celebrity, viz., Hnu to colour a map ivith four colours without 

 colouring adjacent districts the same colour, has just been obtained 

 by Mr. A. li. Kempe, and will shortly appear at length in the 

 American Journal of Mathetnatics. The fact that a map could 

 be so coloured was stated by Prof. De Morgan to be well-known 

 to map-makers, but no proof of the fact or means of solving the 

 problem have hitherto, it is believed, been given. Some notion 

 of the difficulty involved may be gathered from the fact that a 

 very slight alteration in a map may render it necessary to rec«lour 

 it throughout. Mr. Kempc's solution may be roughly described 

 as follows : — He points out that every map must have a district 

 in it w ilh le»s than six surrounding it. This district he gets rid 

 of by putting a patch over it which just projects over its boun- 



daries, all boundaries which meet the patch being produced to 

 meet in a point on the patch. A new map is thus obtained 

 having one district less. This map must also have a district 

 with less than six surrounding it which can be patched out in the 

 same way. Continuing this process the map can at last be 

 reduced to a blank sheet composed of overlapping patches. This 

 can be coloured with a single colour. Stripping off the patches 

 in the reverse order and colouring the districts as they are ex- 

 posed, Mr. Kempe shows that whenever the 1, 2, 3, 4, or 5 

 districts surrounding a newly exposed one absorb all four colours, 

 the colours can be rearranged in the map so as to reduce the 

 surrounding colours to three, thus leaving a fourth for the expo:ed 

 district. Thus successively taking off patches, rearranging the 

 colours in the map, if necessary, a.\d colouring the exposed dis- 

 tricts, the whole map can be coloured. Mr. Kempe also shows 

 inter alia that while the theorem is true in the case of globular 

 surfaces as well as in that of maps, it does not hold in the case, 

 of such a surface as an anchor-ring. 



We have received a copy of the second part of Mr. W. B. 

 Hemsley's "Diagnoses Plantarum Novarum Mexicanarum et 

 Centrali-Americanarum." We believe that the whole of the 

 MSS. of the Polypetala: o( the botany of Messrs. Godman and 

 Salvin's "Biologia Central! -Americana," is now in the hands 

 of the printer, and Mr. Hemsley is far advanced with the 

 Gamopetalcc, The first part of the Polypetala; will shortly 

 appear. The publication of the Polypetala has been delayed, 

 in order to include a very valuable collection made last year 

 in the State of San Luis Potosi, Mexico, by Drs. Parry and 

 Palmer. 



A SERIES of interesting experiments with the electric light 

 commenced, by order of the authorities, at the School of Military 

 Engineering, Chatham, on Thursday last. The experiments are 

 for testing the relative qualities of the several inventions now va 

 use in the Army and Navy, including Messrs. Wylde's invention 

 (which has been fitted on board nearly all the larger ironclads in 

 the Navy), Messrs. Siemens' invention, the Gramme light, and 

 others. The experiments, it is expected, will last several weeks, 

 and they will be carried out under the direction of Capt. Ann- 

 strong, R.E., instructor in telegraphy at the School of Military 

 Engineering. 



The Council of the Institution of Civil Engineers have recently 

 made their annual awards, out of special funds bequeathed for the 

 purpose, for approved original communications read and dis- 

 cussed at the weekly meetings during the past session, or printed 

 in the " Minutes of Proceedings " without being read, as well as 

 for papers submitted by students. From the Telford Fund 

 medals and premiums have been bestowed on Messrs. G. F» 

 Deacon, J. B. Mackenzie, J. N. Douglass, A. F. Blandy, E. 

 Dobson, J. Price, J. E. WilUams, G. W. SutclifTe, E. Sang, 

 W. G. Laws, and G. Iliggin. The Manby Premium has fallen 

 to Mr. J. P. Griffith. Miller Prizes have been adjudged to the 

 following students : — Messrs. A. C. Hurtzig, R. H. Read, J. C. 

 Mackay, and P. W. Britton. 



The fourth marine excursion of the Birmingham Natura'- 

 History and Microscopical Society to Falmouth, which extended 

 from July 5 to 14, has proved a great success, and quite equalled, 

 if not surpassed, the preceding ones to Teignmouth and the- 

 Island of Arran. A larger number of members than usual 

 joined the party, which consisted of nine ladies and twenty-two 

 gentlemen — a total of thirty-one. As hitherto the excursion was 

 arranged so as to give facilities for the study of the marine 

 zoology, botany, and geology of the district. For the former of 

 these an admirable little steam tug, the Albert, was engaged. 

 Land excursions were also arranged daily to interesting points, 

 including the Land's End, the Lizard, &c. For the first time 



