June 7, 1900] 



NA TURE 



-^zi 



of the College of Agriculture of Tokyo "contains an interesting 

 contribution to this question by Dr. U. Suzuki. Experiments 

 were carried out with several species of plants and in soils con- 

 taining varying amounts of calcium. The results show that 

 strontium and barium can never replace calcium in phanerogams, 

 as they are strongly poisonous, although the poisonous action 

 may be lessened to a certain extent by the addition of lime 

 salts. The Bulletin also contains papers by the same author 

 •on arginin, and its formation in coniferous plants; and by 

 K. As5, on the chemical composition of the spores of Aspergillus 

 Oryzae. 



Amongst the products of the action of fluorine upon sulphur 

 ■recently investigated by M. H. Moissan (see Nature, April 19, 

 vol. Ixi. p. 597), thionyl fluoride, SOFj, the existence of which 

 was first indicated by M. Meslans, was noticed. MM. Moissan 

 and Lebeau have now made this fluoride the subject of a more 

 ■detailed study, and have succeeded in obtaining it in a pure 

 state by two diff"erent methods — by the action of fluorine upon 

 thionyl chloride, and by the interaction of fluoride of arsenic 

 upon thionyl chloride. Thionyl chloride is a colourless gas, 

 fuming slightly in moist air, and possessing an unpleasant odour 

 resembling carbonyl chloride. It is easily condensed by a 

 mixture of solid carbon dioxide and acetone, giving a liquid 

 boiling at - 32^. In the absence of moisture, glass is not at- 

 tacked by the gas at temperatures below 400° C. ; above this 

 temperature silicon tetrafluoride and sulphur dioxide are pro- 

 <luced. Water decomposes thionyl fluoride slowly at ordinary 

 temperatures, giving hydrofluoric and sulphurous acid. Indica- 

 tions were obtained of another oxyfluoride of sulphur, not 

 absorbed by water and possessing a much lower boiling point. 



The additions to the Zoological Society's Gardens during the 

 past week include two Wild Swine i^Siis scrofa, ? 9 ), European, 

 presented by the Lord Carnegie ; three Chaplain Crows ( Corvus 

 capellanus) from Southern Persia, presented by Mr. B. T. 

 Ffinch ; a Herring Gull [Lams argentatus), European, pre- 

 sented by Mr. J. W. Berry ; two Red Howlers {Mycetes 

 seniculus, <J 9 ) from Colombia, a Great Kangaroo {Macropus 

 giganteus^ S ) from Australia, an American Flying Squirrel 

 {^Sciuropterus volucella), three American Box Tortoises {Cistudo 

 '■arolttia), a North American Trionyx ( Trionyx ferox), three 

 Changeable Tree Frogs {Hyla versicolor) from North America, 

 a Black Sternothere {Stemothoertis niger) from West Africa, 

 two Greek Tortoises {Testudo graeco). South European; six 

 Argentine Tortoises ( Testudo argentina) from the Argentine 

 Republic, a Red and Yellow Macaw {Ara chloroptera) from 

 Souih America, two Black-headed Caiques {Caica inelano- 



cp/iala) from Demerara, a Chough {Pyrrhocorax graculus), 

 British, deposited ; two Brown Mynahs {Acridotheres fuscus) 

 from India, a Brown Mock Thrush {Harporhynchus ru/iis) from 



forth America, an Occipital Blue Pie {[/rocissa occipitalis) from 

 Western Himalayas, purchased; two Thars {Capra jein- 



ticus), five Swinhoe's Pheasants {Euplocamus szuinhoii), bred 

 the Gardens. 



OUR ASTRONOMICAL COLUMN. 



Photographic Observation of Eros.— A circular from 

 le Centralstelle at Kiel furnishes particulars of the photograph 

 f the planet Eros obtained by Prof. Howe, of Denver 

 )bservatory, U.S.A., during the recent total eclipse. The 

 )sition determined was : — 



R.A. 23h. 47m. 3-9S. \ 

 Decl. + 2° 46' 33" / 



1900 May 27-9129. 

 Greenwich Mean Time. 



Occui.TATiON of Saturn.— There will be an occultation of 

 Saturn by the moon on Wednesday evening, June 13, the 

 particulars of which are as follows : — 



NO. 



1597. VOL. 62] 



The planet rises about 8.55 p.m., so that the conditions for 

 observation will not be very favourable. 



Harvard College Observatory.— In Circular No, 50 

 issued from the Harvard College Observatory, Prof. E. C, 

 Pickering reviews the methods adopted in the measurement of 

 photographic light intensities. Since 1887 all the photographs 

 obtained at the Observatory have had the image of a standard 

 light impressed upon them for comparison. The methods now 

 adopted have been developed by Mr. E. S. King, under whose 

 direction the photographs are taken at Cambridge, and his 

 description of the plan followed occupies the greater part of the 

 circular. All sources of light, that of the sun, moon, sky, 

 Milky Way, aurora and stars are to be referred to one standard, 

 given by the meridian photometer, with which Polaris has a 

 magnitude of 2' 15. The artificial standard for practical con- 

 venience is that given by an Argand burner behind a small 

 aperture ; but this is compared with Polaris every month, when 

 a series of tests are made on a 8 x 10 in. plate, the various parts 

 of which are then cut and stored for future inspection. These 

 monthly comparisons in addition furnish a valuable check on 

 the constancy of the plate and the developer used, and will, 

 moreover, as the several parts of the divided plate are developed 

 at different periods, furnish data concerning any change in the 

 image dependent on the interval between exposure and develop- 

 ment. Spectroscopic photometry is also adopted to record the 

 photographic intensity in terms of light of a particular wave- 

 length. 



Prof W. H. Pickering has evolved a method of reducing the 

 standard of comparison to the actual radiation received from a 

 certain star shining directly on the plate. This unit, however, 

 being so small, secondary and tertiary standards have been 

 made from it by using lenses of known aperture and focal 

 length. Thus, with a simple plano-convex lens of 8*2 cm. 

 aperture, the image of o Ursae Minoris was received on a piece 

 of ground glass placed 3 cm. from the photographic plate. The 

 "sensitive tint" was produced after twenty minutes' exposure, 

 and the intensity of the light was calculated to be thirty times 

 greater than the direct radiation from the star. For lights of 

 great intensity this secondary standard is still too small, and 

 then recourse is had to the Argand burner constant. 



Liverpool Observatory. — We have received the report of 

 Mr. W. E. Plummer, the director of the Liverpool Observatory 

 at Bidston, Birkenhead, on the work done in the year 1899. 

 Although the seismograph has not been in use all the year, it is 

 intended to commence keeping a continuous record of earth 

 movements by means of the present instrument and one to be 

 supplied by the Earthquake Committee of the British Associa- 

 tion. The two will be placed so as to record movements in 

 planes at right angles to each other. 



The report contains detailed results of all meteorological ob- 

 servations during the year, including temperature, barometric 

 pressure, rainfall, sunshine and cloud, wind velocity, humidity, 

 &c. ; and an appendix is added containing a summary of the 

 mean values of many of these quantities during the past thirty 

 years. 



Temperature Control of Spectrograph. — In the 

 Astro- Physical Journal (vol. xi. pp. 259-261, 1900), Prof. W. W. 

 Campbell describes the arrangement he has finally adopted 

 for securing as complete uniformity as possible of the temperature 

 of the various parts of the spectrograph used at the Lick 

 Observatory for determining stellar velocities in the line of sight. 

 The whole instrument is first enclosed in two thicknesses of 

 thick grey blanket, the prism case having an additional two 

 thicknesses over it. Outside the whole is then fitted a case of 

 cedar, lined with felt, in which is embedded a length of German 

 silver wire. This latter is heated by an electric current, the 

 strength of which is so regulated that a thermometer placed in 

 ihe prism box shows as constant reading as possible. The 

 efficiency of the device is clearly shown by a table giving the 

 actual variations observed during a night's work. From 8.28 

 p.m. to 4 a.m. the temperature of the air in the dome varied 

 from i7°-2 C. to 19° o C, but the extreme readings of the ther- 

 mometer in the prism box were only i8°70 C. and i8"84° C.,so 

 that the maximum variation was less than one-fifth of a degree. 



