70 



NA TURE 



[May 1 6, 1901 



after it had become nebular, but associated with these lines in 

 his record is the chief nebular line at 5007, no trace of which 

 is yet visible in the photographs of the spectrum of Nova 

 Tersei. On the other hand, Hfl, which is the brightest line in 

 the present spectrum of Nova Persei, does not appear at all in 

 von Gothard's spectrum of Nova Auriga". 



In the former paper the structure of the broad bright lines of 

 hydrogen was referred to. A more detailed CNamination of the 

 lines as photographed on several evenings shows that this 

 structure has been undergoing changes. 



The annexed figure (Fig. i) gives light curves showing the 

 variation in the loci of intensity of the line H^, as photographed 

 with the 6-inch prismatic camera. These curves were plotted 

 by Messrs. Baxandall and Shaw independently of each other, 

 and I have satisfied myself of their accuracy. It will be seen 

 that on February 25 there were three points of maximum 

 luminosity, the two maxima on the blue side being of equal 

 intensity, and greater than the third on the red side. By 

 March I the centre one had greatly been reduced in intensity, 

 and on the 3rd it had been broken up into two portions, thus 

 making four distinct maxima. 



Rough measures made on the relative positions of these 

 points of maxima show that the difference of velocity indicated 

 lietween the two external maxima is nearly 1000 miles per 

 second, while that between the two inner maxima is 200 per 

 second. We thus have indications of possible rotations or 

 spiral movements of two distinct sets of particles travelling 

 with velocities of 500 and 100 miles per second. 



A similar examination of the F and G lines of hydrogen in 

 the photographs obtained with the 30-inch reflector has also 

 been made by Dr. Lockyer. In this longer series the most 

 important point comes out that the maximum intensity changes 

 from the more to the less refrangible side of the bright 

 hydrogen line 



" On the Electrical Conductivity of Air and Salt Vapours." 

 By Harold A. Wilson, D.Sc, M.Sc, B.A., Allen Scholar, 

 Cavendish Laboratory, Cambridge. 



The experiments described in this paper were undertaken 

 with the object of obtaining information on the variation of the 

 conductivity of air and of salt vapours with change of tempera- 

 tu»e, and on the maximum current which a definite amount of 

 salt in the form of vapour can carry. They are a continuation 

 of the two researches on the same subject published in the Phil. 

 Trans, for 1S99. 



The method employed in the experiments described in the 

 present paper was the following : — 



A current of air containing a small amount of a salt solution 

 in suspension in the form of spray was passed through a plati- 

 num tube heated in a gas furnace ; this tube served as an 

 electrode, and the other was fixed along its axis. The tempera- 

 ture of the tube was measured by means of a platinum platinum- 

 rhodium thermo-couple, and the amount of salt passing through 

 the tube was estimated by collecting the spray in a glass-wool 

 plug. 



The variation of the current at constant E. M.F. with the 

 temperature for air was found to be approximately capable of 

 being represented by a formula of the type C = A6", where C is 

 the current, 9 the absolute temper.ature, and A and n constants. 

 The const.ant « depends on the E.M.F. used. With 240 volts 

 it was 17, and with 40 volts 13. The current, therefore, does 

 not begin suddenly when the temperature is raised, but always 

 increases regularly with the temperature, so that the lowest 

 temperature at which the current can be detected depends 

 entirely on the sensitiveness of the galvanometer. 



The relation between the current and temperature for salt 

 vapours was found to be rather complicated. With KI, using 

 an E.M.F. of 800 volts, the current had the following values 

 (I = 10"^ amperes). 



Temp. 500° 600° 700° 800° 900" 1000' 1 100' 1150° 1200° 1300° 

 Current 07 I'S 3'0 40 4-5 4-0 3.5 3'6 7'0 70 



Thus the current has a maximum value near 900° C, and 

 rises very rapidly near 1 1 50". Similar results were obtained with 

 other salts. 



The maximum current carried by the salt vapour (at 1300' 

 with 800° volts) was found to be nearly equal to that required 

 to electrolyse the same amount of salt in a solution. This fact 

 must be regarded as considerable evidence in favour of the view 

 that the ions are of the same nature in the two cases. 



NO. 1646, VOL. 64] 



Linnean Society, April 18. — Prof. S. H. Vines, F.R.S., 

 president, in the chair. — Mr. Harting exhibited and made 

 remarks upon a mummified hawk from an Egyptian tomb, 

 pointing out the difference between mummies made at Memphis, 

 which are black, dry and brittle, from the bitumen employed in 

 the embalming process, and those from Thebes, which, like the 

 specimen exhibited, are of a yellowish colour, more flexible, and 

 were prepared with natron, or neutral carbonate of sodium, 

 Na.jCOj, brought from the natron lakes in the Lybian desert. 

 Colonel Swinhoe confirmed the statement that our word 

 "mummy," Fr. iiioim'e, Sp. viomia, was derived from the 

 Arabic mourn, wax, the most expensive process of embalming 

 known to the Egyptians being that in which wax and bitumen 

 were the chief ingredients. — Mr. -Charles Dawson exhibited a 

 hollow flint nodule which had been picked up on the downs at 

 Lewes, and which on fracture was found to contain the desic- 

 cated body of a toad. The flint measured 5A inches in length 

 and 12 inches in circumference, and a small hole at one end 

 indicated the point of ingress for the toad, which must have 

 entered in a very immature condition, and died there after 

 having attained a size too great to permit of its escape. In 

 the discussion which followed, remarks were made by Mr. 



E. T. Newton, F. R.S., Mr. John Lewis, and others, the 

 general opinion being that a modern toad had crept into an 

 ancient flint, and, having lived for a time on such insects as 

 found their way into the cavity, had died there.— Mr. S. Pace 

 exhibited specimens of Moseleya latistellala, ()uelch, the so- 

 called " rugose coral " from Torres Strait. The specimens 

 shown were obtained from the backs of pearl-shells collected in 

 Friday Island passage at a depth of three to four fathoms. In 

 the opinion of Mr. Pace they showed that the so-called coral 

 was really a species of Lithophyllia. — Mr. W. B. Hemsley, 



F. R.S., exhibited the leaves and flowers of two new genera of 

 Chinese trees: (i) Bretschneideria, discovered by Dr. Henry 

 in the province of Yunnan, lat. 23° N., in forests at an elevation 

 of 5000 feet, and bearing pink and white flowers like the horse 

 chestnut, to which it is related ; and (2) Itoa, also a native of 

 Yunnan, growing at a similar elevation and to a height of about 

 twenty feet. The genus, named in honour of a famous Japanese 

 botanist, was stated to be allied to Idesia, Maxiin. , Poliothyrsus, 

 Oliver, and Carrierea, Franch. ,all monotypic genera inhabiting 

 China, but differing from them in certain respects which Mr. 

 Hemsley indicated. — Mr. S. Pace read a paper on the formation 

 and variation of the remarkable cup-shaped corallum of Tur- 

 binaria, on which no observations appeared to have been 

 recorded. This was supplemented by a letter from Mr. H. M. 

 Bernard, in which he offered some critical remarks on the paper 

 which the author had previously submitted to him. Further 

 observations on the bearing of the facts described were made by 

 Prof. Howes.— Messrs. W. B. Hemsley, F.R.S., and H. H. 

 Pearson communicated a paper on the flora of Tibet, based on 

 various collections of high-level plants received at the Kew 

 Herbarium. The country dealt with was described as lying 

 between 80" and 102" lat. and 28° and 29° long. , and having 

 an average altitude of 15,000 feet. Within this area 360 

 species of vascular plants had been collected, and were referred 

 to 144 genera and 46 natural orders. Almost all the orders 

 represented were nearly of world-wide distribution, and none 

 were really local. Of the 360 species only 30 appeared to be 

 peculiar to Tibet. In illustration of the paper a selection of 

 the plants was exhibited ; most of them dwarf deep-rooted 

 herbs, very few annual or monocarpic, and the only woody 

 plant. Ephedra gcrardiaiia, was described as scarcely rising 

 above the surface of the ground. The majority had been col- 

 lected at altitudes varying between 15,000 and 18,000 feet. Mr. 

 C. B. Clarke, F. R.S., in making some observations on the 

 paper, pointed out that the name "Thibet" or "Tibet" was 

 quite unknown to the people who dwelt in the country so-called, 

 and its precise boundaries were even still imperfectly defined. 

 It was convenient, however, to retain a name by which it was 

 known to so many European travellers, and the explorations 

 and collections were making us better acquainted with the 

 country every day. 



Zoological Society, May 7 —Prof. G. B. Howes, F.R.S., 

 vice-president, in the chair. — Mr. Sclater exhibited and made 

 remarks on an original water-colour drawing by Sir Harry 

 Johnston, K.C.B., of the remarkable new Mammal from 

 the Semliki Forest in Uganda, which had been described (from 

 fragments of skin only) under the name Equiis johnstoni, and 

 announced that the complete skin and two skulls from which 



