June 30, 1892] 



NA TURE 



211 



discharge, with the result that he has already increased the 

 amount of combination to lo per cent, of the total amount of 

 air employed. The air is exposed under increased pressure to a 

 series of parallel spark discharges in the same tube. The change 

 of atmosphere is not made continuously, but intermittently, and 

 the gases are expelled from the discharge tube into a large 

 absorption vessel in which the products are absorbed in a solution 

 of water, or of a caustic alkali. Detailed accounts are given in the 

 memoir of the efficacy of the various forms of high tension 

 discharge, and Dr. V. Lepel is now experimenting with the dis- 

 charge from a Topler influence machine with sixty-six rotating 

 plates. Of particular interest are his remarks concerning the 

 probable effect of the high voltage discharges of which we have 

 lately heard so much. He considers it not improbable that by 

 their aid a new mode of producing nitric acid from the atmo- 

 spheric gases on the large scale may be introduced, rendering 

 us altogether independent of the natural nitrates as a source of 

 nitric acid. 



The additions to the Zoological Society's Gardens during the 

 past week include two Macaque Monkeys {Macacus cynomolgus) 

 firom North Borneo, presented by the Rev. Augustus D. 

 Beaufort ; two Small Hill Mynahs {Gracula religiosa) from 

 India, presented by Lieut.-Col. W. S. Hore ; a Chough 

 {Pyrrhocorax graculus) from the Aran Islands, Galway, pre- 

 sented by Miss Balfour ; four Soemmerring's Pheasants 

 {Phasianus sammerringi (J <J 9 ? ) from Japan, presented by 

 Mr. Frank Walkinshaw ; an .^Esculapian Snake {Coluber 

 tesculapii), a Vivacious Snake ( Tachymenis vivax) from Central 

 Europe, presented by Mr. Alfred Scrivener ; a Cayenne 

 Lapwing {Vanellus cayennensis) from South America, two 

 Axolotls {Siredon mexicanus) from Mexico, purchased ; a 

 Ruddy-headed Goose (Bernicla rubidiceps 9 ) from the Falkland 

 Islands, received in exchange ; a Burchell's Zebra {Equus 

 burckellii i) ; a Thar {Capra jemlaica), a Japanese Deer 

 {Cervus sika), born in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



Variable Nebul.^.— Mr. Barnard, \n Astronomische Nach- 

 richten. No. 3097, mentions the cases of two nebulae which he 

 supposes must be of a variable type. The first has a diameter 

 of about i', and appears rather like a comet, the brightness 

 gradually increasing towards the centre, there being no nucleus. 

 Its position for 18890 was R.A. 3h. 56m. 17s., Declination 

 + 69° 30' 38". The other nebula was discovered by him in 

 1888, and was estimated to lie between magnitudes 9 and 10, 

 the stellar nucleus being of the thirteenth magnitude. Subsequent 

 observations made in 1891 showed that this nebula had become 

 considerably fainter (13^ mag.), there being still a faint nucleus 

 visible ; its diameter was estimated as \', while its position for 

 1888-0 was R.A. oh. 37m. 557s., Decl. - 8° 48' 6"-S. 



Variation of Latitude.— Mr. Chandler, toward the latter 

 end of last year, contributed to the Astronomical Journal several 

 articles on the variation of terrestrial latitudes, in which the fol- 

 lowing points were brought out : — (i) This variation is truly 

 terrestrial. (2) The period of revolution, from 1863 to 1885, of 

 the pole of the earth's figure round that of rotation amounted to 

 427 days in a west to east direction. (3) About the year 1730, 

 the length of this period was a little over a year. (4) The 

 velocity of rotation is slowly diminishing. In the present 

 number (267) of the same journal he brings together evidence to 

 establish some further conclusions at which he has arrived, 

 basing them on a very considerable number of series of observa- 

 tions. The results may be briefly summarized as follows : — (a) 

 About 1774 the rate of angular motion of the pole was a maxi- 

 mum with a daily rate of l''*034, and since that period the de- 

 crease has taken place at an accelerating rate, {b) If be the 

 daily angular motion and T the interval in days from September 

 18, 1875, the angular velocity of the polar motion maybe put in 

 the form 



f = o°-852 - 0° -000009 8 T - 0° -000 000 000 132 T*. 



NO. 1 183. VOL. 4.6] 



(<■) The law of the periodic variation may be expressed a^ 

 follows : — ' V 



<f> = <p^ - o"-22 cos [\ + (/ - T)e], 



where T is the time when the north pole of the earth's figure 

 passes the Greenwich meridian, 

 E the number of completed revolutions between a given 



date, I, and the adopted epoch, 

 the daily angular motion, 



<P the instantaneous value of the latitude of a place 

 <^o the mean latitude, ' 



and A the longitude of the same place, 

 the values of T and 6 being obtained from the equations— 

 T = 187s Sept. 18-5 + 422^-56 E + id-034 E- + o'ioo9 E^ 



+ o<^ 000067 E<, 

 = 360, 



when P = 423'! 62 + 2d -0953 E + o<'-o274E2 + od -000268 E3. 



{d) A sensibly constant angular distance between the poles of 

 figure and rotation during the last fifty years has been main- 

 tained. 



{<?) By a comparison of absolute and differential determina- 

 tions the variation is entirely due to zenithal alterations, and not 

 to a simultaneous variation of the zenith and the astronomical 

 pole. 



Comparative Spectra of High and Low Sun.— Mr. 

 Edward Stanford has just published five plates, i6| x 19I inches, 

 in portfolio form, of Mr. McClean's beautiful comparative photo- 

 graphic spectra of the high and low sun from H to A. The 

 collotype prints have been reproduced from the mounted photo- 

 graphs by the Direct Photo-Engraving Company, and are 

 enlarged about 8^ times from the original negatives. Published 

 simultaneously also are his comparative spectral photographs of 

 the sun and metals, extending from above H to near D. The 

 two series include the platinum and iron-copper groups. 



The Coronoidal Discharges. — The discovery of the pre- 

 sence and power of electricity is, comparatively speaking, very 

 modern, and it is only now we are finding out the diversity of 

 results it is capable of producing. The sun being our grear 

 source of heat and light, it is only natural that we should 

 suspect him of having a greater quantity of this form of energy 

 in some way or the other, on a scale, of course, very much 

 greater than ours. In a paper read before the National Academy 

 of Sciences, Washington, and published in the June number of 

 the American Journal of Science, Mr. M. I. Pupin describes 

 a series of experiments that he has been carrying out with regard 

 to electrical discharges through poor media. The apparatus 

 which he used is fully described, so we will only refer to the 

 plates which illustrate the points he wished to emphasize. The 

 illustrations are from photographs of discharges taken under 

 conditions under which the solar coronals observed, and suggest in 

 a very striking manner the phenomena that are usually observed 

 at these times. In one case, when the vacuum was very poor, 

 the discharge started in the form of four large streamers, to- 

 gether with large jets, their distribution over the whole surface of 

 the sphere being more or less uniform. The appearance of the 

 sphere "reminded me very much of the granular structure of 

 the sun's disk, . . . and the very luminous points which 

 appeared from time to time . . . reminded me ... of the 

 sun's faculse." Further experiments regarding the rotational 

 motion of the streamers lead him to conclude that two discharge 

 streamers tended to blow each other out, "owing to the motion 

 of the cooler gas between them, this motion being produced by 

 the enormous heating effect of the discharge." The figures 

 shown are very striking indeed, and represent the general 

 appearances of the corona during eclipses with a remarkable 

 degree of accuracy. 



GEOGRAPHICAL NOTES. 



M. Joseph Martin, well-known on account of his explora- 

 tions in North-eastern Siberia, has died at Marghilan while on a 

 journey in Central Asia. 



The Kalahari Desert has been crossed successfully by a 

 "trek" of 150 waggons from the Rustenburg district of the 

 Transvaal, bound for Mossamedes, where an active Boer colony 

 has been established, a large party having embarked at Cape 

 Town to join the overland division. Later report's nfRrm that 



