326 



NA TURE 



[Feb. 24, 1876 



be resisted by a certain chain, we are using a colloquial and in- 

 accurate expression, Iii<e calling a door heavy when we are not 

 attempting tlie feat of Samson, but merely opening or shutting 

 it, turning it on its well oiled hinges. 



During the present session we have aided ourselves in Glasgow 

 with four very important helps to the teaching of the kinetic 

 system of force-measurement. One is the improvement in 

 nomenclature just referred to. The second is the use of names 

 for the kinetic units of force. The British Association has sanc- 

 tioned the use of the name Dytie for the kinetic unit of force 

 founded on the centimetre, gramme, and second, as units of 

 length, mass, and time respec:ively. Prof. James Thomson has 

 given the name Poundal for the British kinetic unit of force 

 iounded on the foot, pound, and second. The third help is the 

 construction by Prof. Thomson, for the first time, so far as I 

 knoAv, of spring balances for indicating poundals and kilodynes. 

 The fourth aid is Dr. Everett's admirable book on the C. G. S. 

 system of units. J. T. Bottomley 



University of Glasgow, Feb. 7 



Seasonal Order of Colour in Flowers 



I AM very much obliged to Mr. Buchan for his elaborate paper 

 in Nature, vol. xiii. p. 249, on the Flowering of Spring Plants 

 (see my query, N ATI' RE, vol, xiii. p. 129). Although agree- 

 ing with Mr. Pryor that the blue is anticipated by various other 

 colours, yet I think that the method of inquiry by averages is 

 the only basis we can go upon ; and that is the plan I have 

 adopted for some time. I have now a carefully-assorted collec- 

 tion of hyacinths, and I see that the blue and white are coming 

 out nearly together, the red showing as yet no colour whatever. 

 What would be the action of light upon blue or red flowers, if 

 the blue or red ray was carefully excluded, if this could be 

 done ? Would the flower thrive, and if so, would its colour be 

 much altered ? C. E. Heron Rogers 



Retford, Notts, Feb. 7 



OUR ASTRONOMICAL COLUMN 



Variable Stars. — Herr Julius Schmidt publishes (in 

 Astro7i. Nach., No. 2,074) the results of observations of 

 variable stars made at Athens in 1875, amongst which the 

 following may be noted : — 



1, 34 Bootis, a star to which he had directed attention 

 some years since, as certainly variable though observed 

 with difhculty on account of proximity to e, was found to 

 be at a maximum on April 26 — a good determination. In 

 1872 he assigned a period of 369 days from six observed 

 maxima, commencirg 1867, July 31, and as many minima, 

 the first, 1867, November 18, Between the maxima of 

 1867 and 1875, we should have eight periods af about 353 

 da) s. The mean place of this star for the beginning of 

 the present year is in R,A. I4h. 37m. 32s., N.P.D., 

 62° 54'-i. 



2, Mira Ceti. Three curves drawn from comparisons 

 of this star with a and y Ceti and a Piscuim gave the 

 date of maximum, February 275, March i and 3 respec- 

 tively, of which the latter is preierred. Calculatmg from 

 the formula of sines in Schonfeld's second catalogue, the 

 maximum of 1875 is fixed to February 24'2. Observed 

 minimum, October 30, 



3, 7; Geminorum. — The variability of this star was 

 detected by Schmidt in 1865, and has since been con- 

 firmed by Schonfeld, who found for the brighter phase 

 small and not very regular fluctuations, but for the minima 

 a regular diminution and increase, the first continuing 

 about six weeks, and the last perhaps rather longer. This 

 is in near agreement with Schmidt's previous deductions. 

 He had found by comparison with /i Geminorum that r] 

 at times remained constant for several months about the 

 maxima, of which, writing in 1869, he states he had been 

 unable to assign the dates. In 1875, however, two 

 maxima were noted, Feb. 25 and Sept. 23 ; showing an 

 interval of 210 days. The period assigned in the last 

 Manheiro catalogue is 229'i days, Tnis star is of a deep 

 yellow colour. Vaxiation between extremes of 3*2 and 

 4-2. 



4. f Aurigae, — Schmidt collects the results of his com- 

 parisons of the relative brightness of ? and ?j Aurigae, 

 between the years 1843- 1875. The star is irregularly 

 variable within somewhat narrow limits. 



5. u Herculis. — The principal period appears to be 

 about 387 days, but according to Schmidt (A, N, 2,075) 

 the curve exhibits waves of about twelve hours' duration, 

 which are of the greatest depth at the principal minimum, 

 and comparatively shallow at the maximum, and he has 

 given a figure explanatory of what he considers to have 

 been the law of variation between 1875, July 4, and 

 Aug, 29, So unique a case appears to require further 

 investigation, 



6. g Herculis. — This reddish-yellow variable was dis- 

 covered by Mr. Baxendell in 1857, and has been carefully 

 observed by Schmidt. The period, according to Schon- 

 feld, has varied between 40 and 125 days, the star thus 

 resembling in the great irregularity of period the well- 

 known R Scuti, which was discovered by Pigott in 1795. 

 Last year Schmidt's comparisons showed three maxima 

 and two minima, indicating periods yj, 73, and 77 day?. 

 The variation extends through little over one magnitude. 



7. a Cassiopeas. — Of this star Schmidt remarks that 

 the fluctuations of brightness in 1875 were not greater 

 than in the cases of other stars, which are not yet placed 

 upon the variable list. 



8. T Coronas Borealis (Nova 1866). — Mostly ninth 

 magnitude, or rather fainter ; exhibiting sensible varia- 

 tion, but to very small amoun*-. 



9. R Scuti, — Observed maxima on Oc'ober 12 and 

 December 8 give the short period of 57 days. The 

 period entered in Schonfeld's second catalogue is "jvi 

 days. There are great irregularities in the case of this 

 star, not only in the period but in the degree of bright- 

 ness at both maximum and minimum ; the former has 

 been noted between 47 and 57, and the latter between 

 6'o and 8"5. 



Minor Planets, — No, 131, Vala, discovered by Prof. 

 Peters at Clinton, U.S,, 1873, '^^■y 24, has so far been 

 unsuccessfully sought at Poll and Berlin between limiis 

 of — 30m, and -}- 15 m, in respect to the place of the 

 ephemeris apparently founded on Stockwell's elements ; 

 the longitude of perihelion in this orbit differs materially 

 from that given by Knorre's earlier calculation, and pos- 

 sibly a misprint or error of transcription may be the 

 cause of the difficulty, — Prof, Tietjen notifies that the 

 ephemeris of No, 141, Lumen, in the Berliner Jahrbiich 

 for 1878, is vitiated by an error in Astr. Nach., No. 2,030, 

 where w is substituted for tt; the habit of some com- 

 puters of giving the orbital angle between perihelion 

 and node, instead of the longitude of perihelion itself, is 

 certainly not without its inconvenience, and this is more 

 particularly the case wath early orbits of comets. — No. 156, 

 discovered by Palisa, 1875, Nov. 22, has been named 

 Xanthippe.— Nqn elements of No. 15-8 give a period of 

 1,889 days, or 5'I7 years. 



The Saturnian Satellite, Hvperion.— Observa- 

 tions of this faint object made with the 26-inch refractor 

 of the U.S. Naval Observatory on forty nights between 

 1875, June 16 and Nov. 25, appear in No, 2,076 of the 

 Astron. Nach. It is stated that the observations were 

 generally made with difficulty. Prof, Asaph Hall acknow- 

 ledges his obligations to Mr, Marth for his ephemerides 

 of the satellites of Saturn, by which he has endeavoured 

 to facilitate identification of these objects, and which 

 could only have been prepared at an expenditure of much 

 time and trouble. 



THE DATE OF EASTER 



VIZ E revert to this subject with the view to reproduce 



' * the arithmetical rule to find Easter Simday in 



the Gregorian Calendar, which was first given by the 



