68 



NATURE 



[A/ay 1 8, 1882 



heat not sufficient to melt the snow of the year. All the water 

 produced is absorbed and assimilated by the ice-layers ; deep 

 temperature below zero. 2. The glacier adolescent. Summer 

 heat fuses all the snow of winter, and attacks by ablation a part 

 of the ice. All the water of imbibition is absorbed and assimi- 

 lated by the ice ; deep temperature below zero, even at the end 

 of summer. 3. The glacier senile. ± ummer heat is in excess. 

 The water of imbibition exceeds the quantity necessary to re- 

 heating of the ice, which rises to 0°, and the excess of water 

 il >ws away in the glacial torrent. Temperature of the glacier at 

 0° during summer. 



On May 8 three shocks of earthquake were felt at Laibach 

 (Carniola), the first occurring at 9I1. 38m. p.m., the last, at 

 midnight, was the most severe, and, lasting two seconds ; it was 

 accompanied by a loud subterranean noise. 



According to statistics recently worked out, the number of 

 railway travellers killed in France is one in each i,6co,ooo,ooo 

 km. run, which is a distance equal to 40,000 times the length of 

 a voyage round the world. This excursion would la't during 

 3044 years travelling day and night at the rate of 60 kilometres 

 per hour. So that, supposing an average life-time of sixty 

 years for a healthy man, before he could be killed by a railway 

 accident according to the law of probabilities, he v ould have 

 died fifty times a natural death. 



In the Report of the Paris Academy of Sciences for April 24 

 (Nature, vol. xxvi. p. 24) the statement with regard to Piof. 

 Ko coe's paper "On the Equivalent of Carbon determined by 

 Combustion of the Diamond" should read " Representing O by 

 '5'9 6 > C becomes 1 1 "97." In the Comples Rendus it is 11*07. 



The additions to the Zoolog'cal Society's Gardens during the 

 past week include a Bonnet Monkey (Macacusradialus 9 ) from 

 India, presented by Mr. II. B. Hamer ; a Common Paradoxure 

 (Paradoxurus typus) from Java, presented by Mr. F. E. Speller- 

 berg ; a Black-faced Kangaroo (Macropus melanops 9 ) from 

 South Australia, presented by Mr. C. T. II. Bower; two Silver- 

 backed Foxes (Cam's chama) from South Africa, presented by 

 Major-General E. A. Bacon ; two Long-eared Owls {Asia otns), 

 Uritish, presented by Mrs. E. Brewer; two Alligator Terrapins 

 (Chelydra serpentina), a Box Tortoise ( Terrapene, sp. inc.), a 

 Floridan Terrapin (Clcmmys floridana) from North America, 

 presented by Mr. G. E. Manigault ; two Beautiful Finches 

 lEstrchta Mia) from Australia, presented by Mr. J. Abraham. ; 

 an Allen's Galago (Galago a/lcni) from Fernando Po, a Levail- 

 'ant's Cynictis (Cynictis fenicillata) from South Africa, a Com- 

 mon Otter (Lutra vulgaris), British, a Swinhoe's Pheasant 

 (Euplocamus s-vin/ioii 9) from Formosa, five WMte-winged 

 Choughs (Coreorax leucopterus), a Spotted liowcr Bird (C/ilamy- 

 dora maeulata i) from Australia, four Common Sheldrakes 

 ( Tadorna vulpanser 6 £ ? ? ), European, two Talpacoti < iround 

 Doves 'Ckamapelia talpacoti) from South America, purchased; 

 a Bennett's Wallaby (Halmaturus bennetti 6), an American 

 Bison (Bison americanus), bom in the Gardens. 



OUR ASTROiXOMICAL COLUAfA 



The COMET. — On May 12 the comet was within naked-eye 

 vision, and will nightly increase in brightness. Writing from 

 Cuckfieldon May 13 Mr. G. Knott says : "The skv was »ery 

 clear here last night, and I found that 1 could ju,t see the comet 

 with the naked eye, on knowing just where to look for it. I 

 iancy that its visibility must have been in part clue to the- fact 

 that its tail is pretty bright forabout |°. When viewed with an 

 opera-glass its light seemed hardly equal to that of neig 

 -tars ra'ed 67 (,.e. 6J) by Hci s and 6-5 by Argelander in D.M. 

 In the telescope the light of the head seemed about equal to that 

 of a 7 mag. star." Tin, estimate by so careful and experienced 

 an observer of star-magnitudes will furnish a reliable criterion as 



to the future increase in the brightness of the comet, assuming 

 that it follows the ordinary theoretical iule. 



The following orbit has been calculated by Mr. Hind from 

 the observations at Harvard and Albany, U.S., on March 19, 

 one at Paris on April II, and a position obtained at the Royal 

 Observatory, Greenwich, on May 4 : — 



Perihelion passage, 1882, June 10-51851 G.M.T. 



Longitude of perihelion 53 54 23-2 \ Mean Fquinox, 



,, ascending node... 204 53 3 1 -3 J 1882-0. 



Inclination 73 410 232 



Log. perihelion distance 8783187 



Motion — direct. 



By a meridian-observation at Greenwich on May 12 (eight 

 days after the last observation employed for the orbit), which 

 Mr. Christie has caused to be reduced with every precision, the 

 corrections to the computed place were: An . cos 8 = -9" - o ; 

 AS = +28""5. Diflereniial observations at the Collegio Romano, 

 in Rome, on May 10, kindly communicated by Prof. E. Millose- 

 vieh, give Act. cos S = -20" 6, and AS — + 26"'o, parallax and 

 aberration being taken into account. 



The ephemeris subjoined i- calculated from these elements for 

 Greenwich midnight : — 



R.A. Deck Log. dist. Intensity 



h. m. s. „ , from Larth. ofligU. 



May 20 ... 2 S3 31 ... +67 15-1 ... 9-9494 ... 1-67 



21 .. 3 S 49 ... 65 SfO ... 9-9494 



22 ... 3 16 51 ... 64 22-5 ... 9-9496 ... 1-92 



23 ... 3 26 46 ... 62 50-1 ... 9-9502 



2 4 3 35 42 ••• 61 14-2 ... 9-9511 ... 224 



2 5 •■• 3 43 45 ••■ 59 35' 2 •■■ 9"9523 



26 ... 3 51 2 ... 57 S3" 1 ••- 9'9S38 ... 2-64 



27 - 3 57 39 ... 56 8-i ... 9-9557 



28 ... 4 3 42 ... +54 20-6 ... 9-9580 ... 3-18 



Considering that the comet is still at a great angular distance 

 from the perihelion and the heliocentric motion slow, the follow- 

 ing places for the beginning of June can be regarded as 

 approximate only : — 



At Greenwich midnight 



R.A. 



Deck 



Log- 



Intensity 

 distance. of light. 



9-9747 ... 6-o 

 99794 •■• 71 



9-9845 ■• s-s 



9-9902 .. 1 1 -2 



15-2 



22-6 



June 2 ... 4 27T ... +44 35 



3 ... 4 30-8 ... 42 27 



4 ... 4 34'5 •■■ 4° 12 



5 ... 4 37-8 ... 37 51 



6 ... 4 41-2 ... 35 20 ... 9-9965 



7 ... 4 44-8 ... +32 36 ... 0-0136 

 The intensity of light nn May 12, when Mr. Knott made his 

 estimate of the comet's brightness, is here taken as the unit. 



At noon on June 10, the intensity of light referred to this unit 

 is 147, and at noon on June n it is 154. The probability of 

 seeing the comet near the sun on these days is not now so great 

 perhaps as it appeared to be from the earlier orbits. 



At the meeting of the Royal Astronomical Society on the 12th 

 inst., the A'tronomer Royal referred to the absence 

 lines in the spectrum of the comet, ace irding to repealed o' serva- 

 tion at Given >h-h. It will be interesting to watch the comet's 

 development as i' approai hes the sun. 



BINOC'LAR PERSPECTIVE 

 ""THAT a near object, of smdl 1 e, re n a pect -lightly 



different to each one of a pair of e_\e directed upon it 

 Feems ti have been known since the time of Euclid; but not 

 until the present century has binocular vision 1 ecu made a sub- 

 ject of special ■ tudy. 



In 1838 Wheatstone presented a communication on the 

 1'hysiology of Vision U'hi . Transactions. 1838, Part 2, re- 

 printed in Pkii. Magazine, s. 4. vol. iii. April, 1852) M the 

 Koyal Society, in which he described his invention of the reflect- 

 ing stereoscope, by which lays from two slightly dissimilar 

 ictures were conveyed into the right and left eves respectively, 

 producing the visual illusion of binocular relief'. The essential 

 feature of tbi instrument he describes by saying (Pail Mag. 

 April, 1852, p. 245): "The two pictures, or rather their 

 reflected image--, are placed in it at the true concourse of the 

 optic axes, 



In 1S44 I rewster published an essay (Edinburgh Transactions, 



