July 26, 1888] 



NATURE 



505 



Occultations of Stars by the Moon (visible at Greenwich). 



Corresponding 



angles from ver- 



July. Star. Mag. Disap. Reap. tex to right for 



inverted image, 

 h. m. h. m. 00 



31 ... /Tauri 4 ... 23 44 ... o 22f ... 25 297 



Aug. 



2 ... B.A.C. 1351 ... 6£ ... 2 20 ... 3 6 ... 112 205 



2 ... 63 Tauri 6 ... 2 44 near approach 158 — 



4 ... x 3 Ononis ... 6 ... 1 52 ... 2 4 ... 346 319 



4 ... x 4 Ononis ... 5 ... 1 58 ... 2 36 ... 109 195 



t Occurs on the following morning. 



Variable Stars. 

 Star. R.A. Decl. 



h. m. , . h. m. 



U Cephei o 52-4 ... 81 16 N. ... July 30, 20 30 m 



Aug. 4, 20 9 m 

 Algol 3 0-9 ... 40 31 N. ... July 31, 2 24 m 



Aug. 2, 23 13 m 

 U Monocerotis ... 7 25-5 ... 9 33 S. ... ,, 1, M 



U Canis Minoris... 7 35-3 ... 8 39 N. ... July 31, m 



U Virginis 12 454... 6 10 N. ... Aug. I, M 



R Hydra; 13 236 ... 22 42 S. ... ,, 1, m 



S Librae 1455-0... 8 4 S. ... ,, 2,2352//? 



U Coronas 15 13-6 ... 32 3 N. ... ,, 2, 4 o m 



U Ophiuchi 17 10-9 ... 1 20 N. ... July 29, 3 36 m 



and at intervals of 20 8 

 W Sagittarii ... 17 57-9 ... 29 35 S. ... Aug. 1, 1 o m 



Z Sagittarii 18 14-8... 18 55 S. ... ,, 4, 1 o M 



U Sagittarii 18 25-3 ... 19 12 S. ...July 30, o o M 



S Vulpeculae ... 19 43*8 ... 27 1 N. ... Aug. 4, tn 



V Aquilae 1946-8... o 43 N. ... „ 2, 3 oJ/ 



R Sagittte 20 9-0 ... 16 23 N. ... „ 2, ' m 



X Cygni 20 390 ... 35 11 N. ... ,, 4, 1 o m 



T Vulpeculae ... 20 467 ... 27 50 N. ... ,, 2, 2 o /)/ 



>» 3> 3 ° m 



5 Cephei 22 25-0 ... 57 51 N. ... July 30, 2 o M 



M signifies maximum ; m minimum. 



Near 8 Andromeda? 



The Perseids 



Near Persei 



Meteor- Showers. 

 R.A. Decl. 



.. 7 ... 31 N. 

 .. 33 ••• 55 N. . 

 . 48 ... 42 N. . 

 350 ... 52 N. . 



Swift ; streaks. 

 Swift ; streaks. 

 Very swift ; streaks. 

 Very swift. 



GEOGRAPHICAL NOTES. 

 The Mittheiluiigcn of the Vienna Geographical Society for 

 June has a paper by Dr. Hans Meyer on the German East 

 African possessions which is likely to attract some attention at 

 the present juncture. No attempt is made to give either the 

 area or the population of this ill-defined region, which, how- 

 ever, is stated to comprise the central section of the East African 

 coastlands, terraces, and plateaux for a distance north and south 

 of about 550 geographical miles, and 150 east and west between 

 the Swaheli coast and the water-parting towards the Congo 

 basin. It is conterminous towards the north with the new 

 British East African protectorate, from which it is separated by 

 a conventional line passing from Lake Victoria Nyanza in an 

 oblique direction along the north foot of Mount Kilima-Njaro to 

 the coast at about 5" S. lat. below Mombasa. Southwards the 

 frontier is marked by the Rcvuma River, and another conven- 

 tional line running thence west to Lake Nyassa, while on the 

 east side it is made to reach the Indian Ocean, thus apparently 

 absorbing the ten mile zone of coastlands reserved to the Sultan 

 of Zanzibar by the Anglo-German Convention of October 29, 

 1886. It is described as orographically and hydrographically 

 the most diversified region in the whole of Africa, including 

 within its limits the highest summit (Kilima-Njaro) as well as 

 the head-waters of streams flowing, north to the Nile, west to the 

 Congo, and south to the Zambesi basin. Hence it presents a 

 great variety of climate and vegetal ion, but nevertheless, except 

 in a few favoured spots, it is not to be compared in productive- 

 ness with the rich tropical lands of the Eastern Archipelago. Its 

 prospects as a future field of German colonial enterprise are 

 spoken of in depressing terms. Both servile and free labour in 

 the interior are stated to be alike impracticable, and for the 

 present at least it will be impossible to develop any great com- 

 mercial activity except on the fertile and more thickly-peopled, 

 but also mostly fever-stricken coastlands. Hence a foundation 

 for the future development of the colony is stated to have been 



laid by the recently-accomplished transfer of the administration 

 of the seaboard from the Sultan of Zanzibar to the German East 

 African Company's agents. But it is added that even here, 

 without State aid, it will be difficult successfully to compete with 

 their English rivals, who have been longer in possession of the 

 field, and who have at their disposal more capital and resources 

 of all kinds. 



ELECTRICAL NOTES. 

 Kundt {Phil. Mag., July 1888) has determined experi- 

 mentally that there exists a proportionality between the velocity 

 of light, electric conductivity, and conduction of heat in metals. 

 The velocity of red light is proportionately as follows — 



Iron 14-9 



Nickel 12-4 



Bismuth (crystallized) 10-3 



Silver 100 



Gold 71 



Copper (impure) ... 60 



Platinum 15-3 



The order is the same for heat and electricity. These figures 

 were obtained in each instance by determining the index of 

 refraction of each metal, which is the ratio of the velocity of 

 light in vacuo to its velocity in the metal. The actual indices 

 obtained were, for red light — 



Silver 0-27 



Gold 0-38 



Copper 0-45 



Platinum 176 



Thus the velocity of light in silver is ten times that in bismuth. 

 How is the velocity of light affected by temperature ? and how 

 is it changed by a magnetic field ? Kundt proposes to examine 

 these points. 



Prof. Elihu Thomson (U.S.A.) states that he has observed 

 as many as six lightning-flashes very quickly following each 

 other along the same path. He kept his head rapidly wagging 

 during a thunderstorm, and his eyes fixed in one direction. Most 

 people have experienced a peculiar throbbing during a flash of 

 lightning ; and a succession of rapid currents, sometimes forming 

 letters, are observed on telegraphs. A lightning discharge may 

 therefore have the same oscillatory character as the discharge of 

 a Leyden jar. But no trace of such an effect is visible in the 

 photographs of lightning-flashes unless it be the mysterious dark 

 flashes that have b_en recorded. 



Chaperon and Mercadier (Comptes rendus, cvii., June 4, 

 1888) have shown that the periodic incidence of rays of light 

 upon a cell of silver sulphide, H 2 SO.i, and bright silver produces 

 sounds in a telephone by the corresponding variations of E. M. F. 

 They call the effect electro-chemical radiophony. The cell 

 copper-oxide, sodium chloride, copper al.-o forms an electro- 

 chemical radiophone. 



E. G. Acheson {Electrical World, N.Y., July 7, 1888) has 

 made some very useful measurements on the sparking distance 

 in air of alternate currents used in electric light working. He 

 finds that it varies with the capacity of the circuit and with the 

 cube of the E.M.F. It is expressed by 



,/= E ' K 



a 



d being the sparking distance in inches, E and K being in B.A. 

 units, and a a constant = 135. Two thousand volts, with 0-0032 

 microfarad in circuit, sparked about o - 2 inch, and 1000 volts about 

 0'02 inch. These results are very different from those obtained by 

 Warren De la Rue with his great battery, who found that with 

 direct currents 1200 volts sparked across 0012 inch and 2400 

 volts across o - 02i inch, but the capacity present is not given. 



Another of Mr. H. Tomlinson's remarkable papers appears 

 in the Phil. Mag. for July. The chief remarkability of these 

 papers consists in their diffuseness. It is almost impossible to 

 extract the new facts out of them. His terms are peculiar. 

 What is "the specific heat of electricity" which changes 

 sign at varying temperatures ? The conclusion of this 

 long paper appears to be that the temperature at which per- 

 manent magnetism begins to suddenly disappear is not the 

 temperature at which permanent torsion begins to suddenly 

 disappear. We find the mechanical" qualities, viz. hardness, 

 i elasticity, linear expansion, internal friction, tensile strength, 

 j molecular structure, torsion, &c, of iron, steel, and nickel inex- 

 tricably mixed up with magnetic susceptibility and retentiveness, 

 electric resistance and thermo-electric conditions, specific and 

 j latent heat, and varying temperatures. 



