292 



NATURE (2" 



{July II, 1878 



matics Dr. Allman points to such works as Bretschneider's 

 " Die Geometric unci die Geometer von Eiiklides " ; Hankel's 

 "Zur Geschichte der Mathematik in Alterthum und Mittel- 

 Alter " (we are glad to find that oiur author's opinion of this 

 work harmonises with the judgment we ventured to pass upon 

 it in these columns) ; to Hoefer's " Histoiredes Mathematiques " 

 (1874), and to some others with which we are not acquainted. 

 Dr. Allman opens his remarks with stating that " in studying the 

 development of Greek science, two periods must be carefully 

 distinguished. The founders of Greek philosophy — Thales and 

 Pythagoras — were also the founders of Greek science, and from 

 the time of Thales to that of Euclid and the foundation of the 

 museum of Alexandria, the development of science was, for the 

 most part, the work of the Greek philosophers. With the foun- 

 dation of the school of Alexandria, a second period commences ; 

 and henceforth, until the end of the scientific evolution of 

 Greece, the cultivation of science was separated from that of 

 philosophy, and punued for its own sake." In the course of 

 forty-seven pages the investigation of what discoveries and 

 advances are due to each geometer is most carefully and dis- 

 criminatingly done, and the reader is put in full possession of the 

 several authorities, and is thus in a position to try the correct- 

 ness of Dr. AUman's deductions. We shall look forward to 

 the continuation of the present paper which the writer promises. 



At a recent meeeing of the Birmingham Microscopical and 

 Natural History Society, Mr. A. W. Wills exhibited the curious 

 rotifer AMicerta pilula (figured by Mr. Charles Cubitt in the 

 Monthly Microscopical Journal of July, 1 872), which coats its tube 

 with a wall of pellets consisting of its own \excremental pilules. 

 Mr. Wills gave an interesting description of the rotifer, and of his 

 experiments with it. One of the specimens he exhibited had 

 commenced the wall of its tube with the natural pellets, and had 

 finished it first with blue pellets, and lastly with scarlet, accord- 

 ing as he had fed it with indigo and carmine. After the meeting 

 Mr. Wills gave the remainder of his specimens to Mr. Bolton 

 for distribution among his correspondents. 



It is stated on the authority of a native Japanese paper, that 

 the Hakubutsu Kioku (Exposition Bureau) of the Home De- 

 partment proposes to erect a permanent exhibition building at 

 Uyano, on the site of the National Exhibition held last year. 

 It will cover about 700 tsuba of ground, and the frontage is to 

 be 360 feet by 75 feet. On its completion it is intended to close 

 the exhibition at Yamashita. 



Dr. Manzoni, of Bologna, has recently established the 

 identity of the marl deposits of Upper Austria with those of the 

 Renodale near Bologna, and describes eight varieties of echino- 

 derms common to the two formations. Of these one still exists, 

 and another is likewise found in chalk deposits. 



The philosophical faculty of Gottingen has offered two prizes 

 of 1,700 and 680 marks for the best works on the causes affecting 

 the changes in chemical composition of plants of the same spe- 

 cies, such as climate, soil, fertilisation, &c. They must include 

 a critical review of all facts hitherto gathered on this subject, 

 and suggestions as to the best methods for completing our know- 

 ledge in this department, accompanied by the results of inde- 

 pendent, research in the directions indicated. Competitors must 

 forward their work before August 31, 1880, and the decision 

 will be announced March 11, 1881. They can make use of 

 Latin, German, French, or English, 



W. Lange has sought to answer the question whether the 

 silicium present in the sap of plants is in the form of silico- 

 organic compounds, or not, and finds {Ber. d. detdsch. chcm. 

 Gesell., vol. ii.) that it exists exclusively as a hydrate of silicic 

 acid in very dilute solution. 



FURTHER RESEARCHES ON THE SCINTIL- 

 LATION OF STARS 



'X'HE results at which M. Ch. Montigny had arrived with 

 ■^ regard to the influence of the atmosphere upon the scin- 

 tillation of stars (see Nature, vol. xiv. p. 562) have since 

 been thoroughly confirmed by his further researches on this 

 subject. The series of observations now comprises no less 

 than 447 evenings, and the predominant influence of rain 

 upon tlie intensity of scintillation may now be recognised 

 as proved beyond doubt. We may here remind our readers 

 that the intensity of scintillation is measured by the number of 

 changes of colour which the star shows in the scintillometer 

 during one second, and that M. Montigny has first proved that 

 approaching moist weather increases this intensity. The fre- 

 quent occurrence of wet days in the year from August, 1876, to 

 August, 1877, has increased the average intensity from 71 to 76 ; 

 but the following very dry autumn of 1877 brought do^vn the 

 average to 68 for that season. 



M. Montigny has also given continual attention to the relation 

 between the scintillation and the nature of the spectrum of any 

 particular star. He has, as before, classified the 41 stars 

 observed according to the three types of Father Secchi (of which 

 type I. comprises the stars \vith four lines in the spectrum, type 

 II. those with a number of fine lines or indistinct bands, and 

 type III. those with broad bands and black lines), and for each 

 type the new average intensity of scintillation is now given, each 

 star in these comparative researches being reduced to an altitude 

 of 60°. It appears now that the average for the first type has 

 remained exactly the same as found before, while those for the 

 other two types have changed but very little, although the 

 number of observations has now risen from 611 to 3,025. These 

 slight changes arise, doubtless, from the circumstance that the 

 recent observations extend to 108 stars instead of 41. All these 

 observations confirm, in the most definite manner, that fact 

 which has already resulted from the first observations, and which 

 M. Montigny expresses as follows: — "The stars possessing 

 spectra with dark bands and black lines scintillate less than 

 those with fine and numerous spectral lines, and considerably 

 less than those possessing spectra with but a few principal lines.'' 



Reserving the special data regarding the scintillation-intensi- 

 ties and the details of the stellar spectra for a further com- 

 munication, M. Montigny now publishes a series of results 

 respecting the colours of stars, which are of extreme interest. 



The colours which the stars show in the scintillometer change 

 in frequency from one type to another, and even between stars 

 of the same type. For the same star the colours in their particu- 

 lar shades, in their frequency, and in their brightness, are further 

 affected by temperature, the degree of atmospherical moistm-e, 

 and the altitude of the star above the horizon. On the same 

 evening, and under the most favourable atmospherical conditions, 

 the number of colours and their brightness decrease steadily as 

 the star rises in the east, and at a certain altitude they are no 

 longer seen. In the west the reverse takes place, i.e., the 

 number of colours and their brightness increase the lower the 

 star sinks, down to a certain altitude above the horizon, which 

 changes according to the clearness of the atmosphere. If the star 

 rises or sets, the limit at which the colours cease to be distinct is 

 all the lower, both in the east and in the west, the finer and 

 warmer the weather happens to be at the time. If the star has 

 passed beyond this limit in rising or has not reached it in setting, 

 it shows only a circle of a constant colour in the scintillometer, 

 i.e., of the colour peculiar to the star, and thus this apparatus 

 offers an excellent means for determining the colours of stars. 



The colours observed in scintillation are : red, orange, yellow, 

 green, bluish green, blue, and violet. The difference in these 

 colours is characteristic for the different star types, if we neglect 

 the influence of the star's altitude and the condition of the atmo- 

 sphere. Thus the red, which is the most constant colour for the 

 three types, generally approaches the shade between the lines B 

 and C of the solar spectrum in stars &f the two first types, while 

 stars of the third type give either a very dark red, or a bright 

 cherry red, or very deep pink. The blue in stars of the first 

 type is bright, and resembles steel blue in shade, while the blue 

 in stars of the third type often shows a very dark shade, so dark 

 sometimes that it becomes difficult to recognise it. When the 

 weather was rainy the blue seemed generally to predominate 

 amongst the other colours in ail stars. Pure green was 

 not so frequent than the other colours. Violet was also 

 very rare amongst all the stars, but particularly amongst 



