Mav, igo6.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



431 



ASTR.ONOMICAL. 



By Charles P. Butler, A.K.C.Sc. (Lond.), F.R.P.S. 

 Temperature of the Sun. 



M. MoissAN has recently published another section of the 

 results of his investigations on the distillation of various sub- 

 stances in the electric furnace, and that in relation to titanium 

 is specially important for solar physics by reason of the wide- 

 spread occurrence of that element in the solar spectrum, 

 occurring as it does in both chromosphere and sun spots. 

 Unlike boron and carbon, which appear to distil directly into 

 vapour from the solid state, titanmm was found to assume 

 the liijuid intermediate state, and by careful measurements 

 with specially constructed thermometers it is possible to gain 

 an approximate estimate of the temperature of volatilisation. 

 Using a current of 1000 amperes at 55 volts, he found that, 

 starting with 300 grammes of material, after seven minutes 

 about no grammes had been distilled. Various measures of 

 the arc temperature have been made, the best of which is 

 probably that of Violie, who estimates the maximum tempera- 

 ture to be about 3500° C. In transferring this to estimates of 

 the solar temperature, however, the fact must be remembered 

 that the pressure at the sun's surface may be vastly different 

 to our terrestrial atmospheric pressure, and thus the tempera- 

 ture at which a certain metal can exist as vapour may also be 

 greatly modified. 



Terrestrial Shadow Bands. 



An interesting account of the ol)servation of terrestrial 

 shadow bands is communicated to the Bulletin of the I-'rench 

 Astronomical Society by M. A. Chevremont, who was particu- 

 larly struck with their similiarity to the moving shadows seen 

 just before and after the total phase of solar eclipses. 



The observations were made in Ouiberon Bay, during the 

 stay of the North Squadron. During the night exercises the 

 powerful searchlights from the warships repeatedly rested on 

 the white vertical walls of the buildings on shore. The dark 

 bands, very clear, with an undulating motion, were from 10-15 

 cm. wide, and had a motion of 4-5 metres per second. The 

 wall forming the screen was oriented to the East, and was 

 placed perpendicularly to the rays from the projectors, of 

 which the distance was abDut 3.5 kilometres. Under those 

 conditions the bands were displaced from the North to the 

 South. They were best seen at about 10 metres distance. 

 Similar fringes were seen on another wall oriented North-east 

 to South-west, thus being very oblique to the line of rays, 

 and in this case, as before, the shadows moved from right to 

 left. 



R.elation of Solar Prominences to 

 Magnetic Storms. 



Very definite coincidences were observed on several occa- 

 sions during 1905 between the outburst of special prominences 

 and movements of the magnetic needle. 



On January 29, 1905, a very remarkable eruption was 

 observed which appeared to proceed from the centre of the 

 great spot group, then near the east limb, but it was very 

 notable that no metallic reversals were visible. In the same 

 spot region, however, strongly metallic eruptions were detected 

 by Professor A. Fowler on February 2, 1905. Later in the 

 year, on November 10, 1905, Mr. j. Fver.shed observed another 

 metallic eruption at 9I' 15'" to 9'' 35'" a.m., during which the 

 sodium, magnesium, and enhanced iron lines were brilliantly 

 reversed for some time. It is very important to note that the 

 magnctograph records at both Greenwich and Stonyhurst 

 (Observatories show very minute disturbances on February 2 

 and November 10, exactly at the times of active phase of these 

 two metallic eruptions. 



New Catalogue of Bright Stars. 



A most useful catalogue of the brighter stars has recently 

 been published by M.J. Bosssrt, one of the astronomers at the 

 Paris Observatory. The best positions have been adopted for 

 stars in both hemispheres, and brought up to the epoch 1900^ 

 The list contains the co-ordinates of 3800 stars, giving the right 

 ascension and north polar distance ; the limit of magnitude is 

 ye. A rather peculiar but asaful arrangement is that the stars 

 are grouped in zones of i" of polar distance, and then ranged 

 in each group by their right ascensions, instead of the more 

 common one of order of right ascension throughout. A very 

 complete introduction gives all the necessary details and 

 formulaifor computin; ths star places at other epochs. 



BOTANICAL. 



By G. Massee. 

 Desert Vegetation. 



It haslongbeen known that the plants of desert regions possess 

 marked peculiarities, both morphological and physiological, 

 which enables them to retain a foothold under such exceptional 

 surroundings. With the object of investigating these matters 

 under the most favourable conditions the Americans have 

 established a Desert Botanical Laboratory at Tucson, Arizona. 



The water relations of the plants of arid regions are so very 

 delicately adjusted that a very slight variation in the available 

 supply, or in the relative humidity of the air, produces a 

 very quick and notable effect. A shrub called Ocotillo 

 (Foiiqnicria spkndcns) responds quickly to an increase in the 

 water supply. Owing to a long period of drought, a specimen 

 of this plant had, up to June 29, been for several weeks with- 

 out leaves. On June 29 three gallons of water were poured 

 slowly on the ground at the base of the plant ; on July i leaf- 

 buds were observed, which at 2 p.m. on the following day had 

 become i cm. long, and four days afterwards the leaves were 

 full grown. Other plants of Ocotillo showed the same response 

 to an increase in the water supply. 



Palo verde is so called because not only are the leaves 

 green as in other trees, but mainly on account of the green 

 colour of its twigs, branches and stem, all of which are pro- 

 bably capable of giving off water vapour from their surface, 

 and also capable of assimilating carbon dioxide. Palo verde 

 has a low rate of transpiration, and the possible range of 

 transpiration is also small as compared with other desert 

 forms ; that is, the ma.ximum rate in summer, when the leaves 

 are on, is not much greater than the minimum, when the 

 leaves have fallen, as is the case with other desert plants that 

 have been studied. In cases of extreme drought the leaves 

 are shed, consequently the area of transpiration is reduced 

 and the necess.ary adjustment of the rate of transpiration is 

 accomplished. 



The period of activity of plants depends on the period 

 during which they retain their leaves. In the case of desert 

 plants growing under adverse conditions, in addition to the 

 large amount of moisture present in the air — which retards 

 transpiration and thus assists the plant in reserving to some 

 extent the amount of water at its disposal — it is considered 

 probable that the leaves absorb atmospheric moisture in 

 sufficient quantity to be of biological importance. 



It has been proved that stems of Ocotillo absorb both water 

 and atmospheric moisture ; it has also been shown that a 

 branch of Ocotillo without leaves can absorb a sufficient 

 amount of water to induce the formation of leaves. 



Pla-nt Life in Spitzbergen. 



Dr. Wulff, who accompanied a Scientific Mission to Spitz- 

 bergen, paid special attention to the ecological condition of 

 the flora. Transpiration was found to be very feeble and 

 without marked diurnal periodicity. This imperfect transpira- 

 tion is considered as one of the causes of the feeble growth of 

 -Vrctic vegetation. Anthocyanin is present in about half the 

 number of the higher plants. It is always absent from plants 

 growing on soil mi.xed with the dung of wild birds, whereas it 

 is present in the same kind of plants when growing in im- 

 poverished soil. 



Anthocyanin is considered as an absorber of energy, and 

 without it no plant can become dominant in Arctic regions. 



