.S82 



NA TURE 



[April 19, 1894 



in the last number of the Mitteilungen for German protectorates, 

 edited by Dr. Danckelman. Dividing the requisites for a com- 

 plete topography into route surveying, compass bearings, 

 Tieasurement of altitude, and astronomical determination of 

 latitude and longitude, he insists on the importance of all 

 travellers being adequately instructed before setting out, so that 

 they may use their instruments to the best advantage when in 

 the field 



The difficult question of the delimitation of the Congo State 

 in the south-east, where the district of Lunda was in dispute 

 with the Portuguese, has been settled by a commission consist- 

 ing of the Rev. George Grenfell and Captain Gorin for the 

 Congo State, and Lieutenant Sarmento for the Portuguese 

 Government. The work of surveying and settling the frontier 

 was completed in May last year, and the treaty was ratified at 

 Brussels in March 1894. A map and brief report on the con- 

 ditions of the border country are published in the AIoiive?nent 

 Geog7'aphique. The country is richly wooded, and Elais 

 Gtiineevsis is abundant at levels below 2000 feet. The com- 

 mission did not meet with many animals, except on the rivers, 

 and few birds were to be seen. 



The Lubudi, one of the upper tributaries of the Congo which 

 joins the Lualaba about 9° south, was reported by Cameron on 

 the strength of native rumour, and was not properly laid down 

 On the map until the Katanga Expedition of Francqui and 

 Cornet in 1892. An account of the river, with a map, is 

 given in the last number of the Mouvement Geographique. The 

 Lubudi rises on the high land known as Mount Kamea, the 

 southern slopes of which drain to the Zambesi, and before it 

 reaches the Lualaba follows a longer course than the main river 

 itself. The confluence is somewhat remarkable, the two large 

 rivers flowing parallel to each other for about a mile and a half, 

 separated by a narrow strip of low alluvial land. The lower 

 part of the Lubudi only has been explored as yet, although 

 it has been crossed higher up by Mr. Arnott and others. 



An improved form of Blackburn's pendulum for the slow pro- 

 duction of Lissajous's figures has been exhibited before the 

 Istituto di Bologna by Prof. Augusto Righi. The ordinary 

 simple form, in which a cup filled with sand is suspended by 

 two strings joined in the shape of a Y, and the sand traces the 

 compound oscillations about the two centres of suspension on a 

 plate underneath, is unable to exhibit the figures obtained when 

 the two periods are equal. In Righi's modification both the 

 cup and the plate are suspended separately, and oscillate in 

 planes at right angles to each other. By means of a clamp 

 sliding vertically along the support, the cup can be given a great 

 variety of periods, and a graduated scale enables the experimenter 

 to adjust the two periods to any desired ratio. The strewing of 

 the sand is controlled by a small valve at the bottom of the cup 

 worked by an electromagnet, the current being transmitted 

 along the suspending wires. Yhis renders possible a very 

 beautiful modification of the experiment. By making the 

 current intermittent with regular intervals, the lines of sand are 

 broken up into short pieces, whose length represents the velocity 

 of the moving cup with respect to the plate. Another electro- 

 magnetic contrivance enables the observer to fix the exact phase 

 of the vibrating plate at which the cup shall start on its own 

 vibrations. The apparatus may easily be adapted to the com- 

 position of two oblique oscillations, and the curves, which are 

 neat and sharply defined, may be fixed by means of steamed 

 gum or sensitive paper. 



In dealing with refractive index as an aid in the elucidation 

 of chemical constitution, one of the most important questions 

 which has to be answered is how to eliminate or allow for the 

 effect of wave-length. The relationships obtained vary with 



NO. 1277, VOL. 49] 



the colour of the light used. According to Maxwell's theory, 

 for infinitely long waves the square root of K, the dielectric 

 constant, is equal to the refractive index ; v K may therefore 

 be taken as a measure of the "dispersion-free" refractive 

 index. In the Zeits, fiir phys. Chem. xiii. 385, Jahn and 

 Moller give a series of relative values of K for a number of 

 liquids consisting of alkyl and aromatic halogen compounds and 

 fatty acids. The communication forms an addition to that pub- 

 lished by Landolt and Jahn {loc. cit. lo, 289) in 1892, and 

 which dealt with liquid hydrocarbons. The first term. A, in 

 Cauchy's dispersion formula has been generally used as giving 

 the refractive index for infinite wave length. The present work 

 shows, however, that of all the above liquids the paraffins alone 

 give values of Vk which approximate to those of A. The 

 paraffins alone exhibit normal dispersion. Moreover, the values 

 of the molecular refraction as calculated by means of vK 

 differ considerably from those obtained by using A or refractive 

 indices for light of a particular wave-length such as the red 

 hydrogen line. Indeed, isomers which have the same mole- 

 cular refractions for the red hydrogen line may give values which 

 differ considerably when K is used, and in general the values of 

 K are largely influenced by chemical constitution. The com- 

 munications are important contributions to the connections which 

 exist between optical properties and chemical nature. 



A CATALOGUE has been issued of woiks on Italian Litera- 

 ture, Art, Archaeology, and History offered for sale by Mr. 

 Bernard (^uaritch. 



M. A. Klossovsky has prepared a memoir (in Russian) 

 on the climate of Odessa, from observations made at the 

 Meteorological Observatory of the Imperial University. 



The Zoologischer Anzeiger% index to the zoological literature 

 of the second semester of last year has just been published. 

 The titles are classified under forty-one heads ; hence there is 

 little difficulty in finding the various papers. 



MM. J. B. Bailliere et Fils, of Paris, have issued a 

 catalogue of old botanical works (prior to the nineteenth 

 century) and works on the history of botany, comprising more 

 than 1000 volumes and pamphlets. 



Prof. W. Trelease reprints, from the fifth annual report 

 of the Missouri Botanic Garden, a monograph of the American 

 species of two little-known genera of Onagracese, Gayophytum 

 and Boisdiivalia. 



Further papers have been issued by Mr. C. A. Barber on the 

 " Diseases of the Sugar-cane in the West Indies, "and suggestions 

 made for their remedy, which consist chiefly in the selection of 

 those strains which appear to be least susceptible to the disease. 



In Bulletin No. 9 of the Minnesota Botanical Studies is an 

 interesting article by Miss Josephine E. Tilden, on the elaters 

 of the HepaticK, especially of Conocephalus, in which their 

 tendency to branching is described. In a young state the 

 elaters always contain starch. 



Messrs. Bailliere, Tindall, and Cox have re- issued the 

 second edition of Mr. Henry Penning's " Text- Book of Field 

 Geology," published in 1879. The book contains a section on 

 Palaeontology, by Mr. A. J. Jukes- Browne. 



Messrs. BAiLLifeRE have also published a fourth edition of 

 Mr. C. T. Kingzett's " Nature's Hygiene," the first edition of 

 which appeared fourteen years ago. The book has been care- 

 fully revised, and a chapter has been added on the subject of 

 phagocytosis and immunity, as well as one on alimentation and 

 foods. 



