620 



NATURE 



[October 26, 1893 



pression bordered by the highest summits in Japan, and occu- 

 pied by a girdle of volcanoes. Ed. Suess (" Anilitz d. Erde," 

 bd. ii. p. 225) and the Japanese geologist, Harada, are of 

 opinion that the mountains in the north and south wings belong 

 to two independent chains which during the period of upheaval 

 had been pushed against one another at this " fossa magna, " and 

 they compare the case of Hindu Kushand the Himalayas. Dr. 

 Naumann still adheres to the view he had previously advanced, 

 namely, that the mountains of the north and south wings form 

 one chain, which after its upheaval was broken by a transverse 

 fault along the "fossa magna," the transverse fault being of 

 later date than the main longitudinal fault on the west or inner 

 side of the islands and cutting through it. The eruptive activity 

 and frequent subsidences within the " fossa " have merely taken 

 advantage of this important tektonic break. 



The Report on the Botanic Gardens at Georgetown, British 

 Guiana, for the year 1891-92, contains some interesting informa- 

 tion on the meteorology of that colony for the year 1891 . The 

 rainfall was much above the average, though not so much so as 

 in the two previous years. For the -nine years ending 1S88 

 the average fall was 805 inches, but for the three years ending 

 1891 the average fall has been II9'6 inches ; the returns from 

 various stations show that there is a gradual increase in the 

 rainfall from the south to the north of the colony. The 

 number of days on which the sun shone was 351, leaving only 

 14 days of unbroken cloudiness ; the mean daily sunshine for 

 the year was 7h. 13m. The maximum day temperature in 

 the shade ranged from 84° in February to 90° in September and 

 October. The minimum night temperature ranged from 71° to 

 74°, and the solar radiation from 148° to 157°. 



A CAREFUL study of the vapour pressures of aqueous solutions 

 has been carried out by C. Dieterici, of Breslau, who has cota- 

 municated his results to Wiedemann s Annalcn. The deter- 

 minations were made for 0° C. by means of an apparatus de- 

 signed for the appreciation of very feeble pressures. The gauge 

 used was an aneroid box with a German silver disc, which has the 

 advantage of yielding to a great extent without elastic fatigue. 

 The motions of the centre of the disc were transferred to a 

 mirror suspended in jewelled bearings by means of a light watch- 

 maker's arbor, the connection being made by a cocoon thread, 

 and the mirror being gently held in position by a small spiral 

 spring. Deflections were measured by reflected scale and tele- 

 scope. The gauge was fitted to a tube which could be filled 

 with the vapour of the solution surrounded by melting ice, or 

 could be exhausted at pleasure. The gauge and tube were 

 enclosed in another air-tight space which could be filled with 

 pure water vapour at 0° C. or exhausted. The pressure of the 

 water vapour produced a deflection of 170 scale divisions, 

 equivalent to 2 '3 1 mm. of mercury. The author discusses at 

 length the bearing of his results upon Van't HofTs dissociation 

 theory, and upon the kinetic theory of gases. The curves 

 exhibiting the relation between degree of concentration and the 

 corresponding vapour pressure have the common characteristic 

 that with the concentration increasing from an infinitely dilute 

 solution to about 26 in multiples of the normal solution, they 

 commence at approximately the same angle, then fall with a 

 steep incline, and finally tend to become parallel to the axis of 

 abscissae. At about 25 the curve of sulphuric acid cuts this axis, 

 showing that the action between the acid and the water counter- 

 balances the osmotic pressure necessary for evaporation. The 

 other bodiei investigated were glycerine, phosphoric acid, and 

 the hydrates of potassium and sodium, enumerated in the order 

 of decreasing vapour pressures. 



The current number of the Philosophical Magazine contains 

 an account of the most recent determinations of the refractive 

 indices of liquid nitrogen and air, carried out by Profs. Liveing 



NO. I2S2, VOL, 



48] 



and Dewar. Owing to the bubbles constantly rising from liquid 

 nitrogen, the prism method could not be made to give accurate 

 results. The refractive index was therefore determined by 

 finding the angle of total reflection. The liquid nitrogen, or 

 air, was enclosed in a cylindrical vessel containing two vertical 

 plane-parallel plates of glass with a film of air between them. 

 The light from an electric discharge or a monochromatic flame 

 was sent through a slit into the vessel, a suitable portion being 

 cut off by black paper screens, and an image of the slit was 

 thrown upon the slit of a spectroscope by the glass vessel itself. 

 The vertical plates were turned round a vertical axis till the ex- 

 tinction of the image indicated that the angle of total reflection 

 had been reached . The refractive index thus obtained for sodium 

 light was I 226 in the case of liquid oxygen (the prism method 

 gave I "2236), 1-2062 for liquid air, and 1-2053 for liquid nitrogen 

 at - 190°, and of density 0-89. The nitrogen probably contained 

 5 per cent, of oxygen. The refraction constant of nitrogen is 

 therefore o 225 as determined from the liquefied substance. 

 Mascart gives o 237 for the constant as determined from gaseous 

 nitrogen. The two results are in as fair an agreement as 

 could be expected, considering the difficulties surrounding the 

 measurements. 



Wiedemann's Annalen de Physique et de Chemii for October 

 contams a paper, by R.J. Holland, on electrical conductivity of 

 copper chloride solution. The solution, whose resistance was 

 to be measured, was enclosed in a dumb-bell shaped glass vessej 

 about 10 cm. long, the electrodes, which had a surface of 

 2i sq. cm., being fixed at the ends. In order to determine the 

 mean section of the tube between the electrodes, it was filled 

 with a solution of sodium chloride and the resistance 

 measured, then using Kohlrausch's results for the resistance of 

 the salt solution the mean section was calculated. The resist- 

 ance was measured by means of a Wheatstone's bridge, with 

 an alternaiing current and telephone. All the strengths 

 of copper chloride solution examined show a regular, though 

 slight, increase of conductivity at high temperature, this in- 

 crease being different for solutions of diUferent degrees of 

 concentration. The maximum conductivity was obtained with 

 a solution containing about 18 per cent, of the dried salt. The 

 temperature coefficient varies with the degree of concentration, 

 and attains a maximum value for a temperature of about 40° C. 

 When the dilTerence in concentration is taken into account, the 

 results obtained agree very well with those obtained by Trotsch 

 and Wiedemann, though they do not show so satisfactory an 

 agreement with those obtained by Isaachsen. 



V Elcttricista for October contains a paper by Dr. Monti, in 

 which he gives the results of the experiments he has undertaken 

 in order, if possible, to account for the fact that the values 

 obtained by Macfarlane in 1877 for the difference of potential 

 required to pierce a plate of paraflSn were very much smaller 

 than those obtained by Steinmetz and himself. Macfar- 

 lane found that the difference of potential required to 

 pierce a plate of paraffin 3 mm. thick was 39,000 volts, 

 while Dr. Monti finds that to cause a discharge to pass 

 between two knobs 5 mm. in diameter through a layer of 

 parafiin I mm. thick it requires a difference of potential of 

 155,000 volts. The author employed paraffin which melted 

 at 5476° C. The terminals were brass balls which were fixed 

 within a glass tube about 10 cm. long. Their distance apart 

 having been measured by means of a microscope, the paraffin 

 was melted and allowed to cool in a partial vacuum. It was 

 then again melted and allowed to solidify under the ordinary 

 pressure. By this means the formation of air bubbles within 

 the paraflin was avoided, and it is to the presence of such air 

 bubbles in the slab of paraffin employed by Macfarlane that Dr. 

 Monti attributes the difference in the values obtained. 



