66 



NATURE 



[May 19, 1887 



decide whether such claim is justifiable. He discusses, the 

 evidences on which lakes may be regarded as of marine origin — 

 historical, morphological, biological, and with regard to exist- 

 ing names. Pie then devotes considerable space to the dis- 

 cussion of the claims of lakes in all parts of the world to be 

 regarded as of such origin ; to the relations between salt- and 

 fresh-water fauna ; and to a critical examination of the faunistic 

 argument for the marine origin of existing inland lakes. He 

 concludes that none of the arguments derived from the con- 

 siderations referred to have a convincing importance in deciding 

 as to the marine origin of lakes. Dr. Credner is of opinion 

 that the question can only be satisfactorily solved on the geo- 

 logical evidence furnished by the various lake regions ; and 

 this argument he means to develop in a second part of this 

 very valuable monograph. 



Details are to hand of the recent exploration of the Mobangi 

 tributary of the Congo, by Capt. van Gele, which add some- 

 thing to the results obtained by Mr. Grenfell. Capt. van Gele's 

 journey was made at the end of 1886, at the time when the 

 river is in flood, and when the current of the rapids is most 

 powerful. At no part was the water less than i "So metre in depth, 

 and the deepest did not exceed 1 1 metres. Not far from the embou- 

 chure of the Mobangi, on the left bank, 8'3o''S. lat., I7°35'E. long., 

 there is a French station. Above this part the Mobangi measures 

 2500 metres in breadth, ii metres in depth in the centre, with a 

 current at the rate of i metre per second. At the 4th degree N., 

 just below the rapids, there is a breadth of 1200 metres, a 

 depth of 7*50 metre-, and a current of 1*50 metre per second. 

 Between these two points the breadth of the Mobangi constantly 

 varies, never exceeding 40CO metres. Its waters are of a clear 

 brown colour, and its general aspect much the same as that of 

 the Congo, its channel studded with islands, and its banks 

 wooded. The right bank is often marshy, while the left bank 

 is frequently steep, and the neighbourhood hilly. The left bank 

 is much more densely peopled than the right, which never has but 

 a scanty population. On the left bank, especially above the 2nd 

 degree of latitude, there is a rapid succession of villages, belonging 

 to the Baati, the Monyembo, and the Montumbi. The people are 

 well made and tall (mean height of men i 'So metre), they are 

 industrious, but at the same time inveterate cannibals. In all 

 the course of the river which has been observed, Capt. van Gele 

 did not notice any affluent of importance ; the only three worth 

 mentioning are the Nghiri on the left bank, and the Ibenya and 

 the Lobay on the right. The Nghiri winds through a very 

 marshy country, which probably occupies the place of the con- 

 jectural lake of that name. About 4° N. lat., a mountain 

 mass is met with, running in a north-east and south-west direc- 

 tion, through which the Mobangi must penetrate in making its 

 way to the Congo, and here it is, as might be expected, that 

 rapids are found. The river here is narrowed into a gorge, 

 impassable at high water, but, Mr. Grenfell assures us, quite 

 passable at low water for a suitable steamer. 



The Argentines have been very active recently in the explora- 

 tion both of Patagonia and of their section (the eastern) of 

 Tierra del Fuego. In a communication which appears in Peter- 

 manns Mitteilungen, Ram.on Lista gives some details of a 

 journey which he made [through the centre of the large 

 eastern island from Sebastian Bay to the Strait of Le Maire. 

 He states that our notions of the surface and climate of this 

 island have hitherto been entirely erroneous : it has been re- 

 garded as inhospitable, barren, and uninhabitable ; its rocky 

 mountains covered with everlasting snow. This may be so with 

 the west part of the land, but M. Lista gives a different account 

 of the region traversed by him. From Cape Espiritu Santo to 

 Cape Peiias he found valleys of varying breadth, covered with 

 luxuriant fodder plants, and abounding in rivers, some of which 

 are navigable, and which come from a snow-covered region 

 in the interior. South of this is found the region of Antarctic 

 forests. Though not so rich in grass and water as the northern 

 region, M. Lista states that it made a favourable impression on 

 him. He saw a good deal of the native population, and collected 

 considerable data as to their anthropology. Many other scienti- 

 fic observations were made by him on the geology, fauna, and 

 flora of the country. 



The Carniola section of the German and Austrian Alpine 

 Club has resolved to put up on the Old Posthouse at Wurzen, 

 the favourite head-quarters of Sir Humphry Davy, a tablet to 

 commemorate his services in making known the South-Eastern 

 Alps of Austria, and in attracting visitors thither. 



THE ROYAL SOCIETY CONVERSAZIONE. 



T AST week we referred to the conversazione of the Royal 

 -^ Society, held on Wednesday, the lith inst. It was the 

 best which has been given for many years. A large number of 

 remarkable objects were exhibited, and an account of some of the 

 most important of them may be of interest to our readers. 



Prof. A. W. Riicker exhibited lecture apparatus to illustral 

 the measurement of coefiicients of expansion by means ot 

 Newton's rings. The rings are formed between a glass plate 

 and the convex end of a glass cylinder. These are pressed to- 

 gether by a metal frame, the front and back of which are con- 

 nected by tubes through which a current of water is passed. 

 The rings are projected on a screen and expand or contract when 

 the temperature of the water is altered. The apparatus was 

 shown in operation. 



Maps to illustrate the present state of the magnetic survey of 

 the British Isles now in progress, with a set of instruments of the 

 Kew pattern, which have been used in the survey, were exhibited 

 by Profs. Thorpe and Riicker. (i) Large map showing the 

 stations at which observations have been made, and the values 

 of three magnetic elements, viz. the inclination, declina- 

 tion, and total force at all places for which the reduction of 

 the observa'ions has been completed. The epoch of the survey 

 is to be January i, 1886, but the values given are not as 

 yet_ corrected for secular change, except in the case of 

 stations in Scotland. (2) Three maps of Scotland showing 

 the lines of equal dip and equal total force for 1837, 1858, and 

 1886, and the lines of equal declination for 1858 and 1886. 

 Mr. C. V. Boys exhibited a radio-micrometer and spinning-pile, 

 which is probably the most sensitive instrument for measuring 

 radiant heat yet made. It consists of a movable circuit of cop- 

 per, antimony, and bismuth hung by a quartz fibre in a strong 

 magnetic field. One-hundred-millionth of a degree is not beyond 

 the possible limit of such an instrument. Prof D'Arsonval 

 made an inslrument essentially the same in principle last year. 

 This radio-micrometer was devised by the exhibitor without 

 knowledge of M. D'Arsonval's, from which, however, it differs 

 in important details. The one exhibited is an experimental 

 instrument only ; but it is about one hundred times as sensitive 

 as a thermopile. The spinnin;7.pile is peculiar in that it will 

 start itself and turn either way indifferently when a spark is held 

 on one side, and will at once stop when the spark is held on the 

 other. Mr. Boys also showed an apparatus for shooting threads 

 of glass, emerald, quartz, &c. A thin rod of the material is fast- 

 ened to the tail of an arrow and heated at the end by an oxy- 

 hydrogen flame. The trigger of a cross-bow is immediately 

 pulled, and the arrow shot, when a thread of extreme fineness is 

 drawn out. These threads are far finer than spun glass, and 

 many are finer than spider- lines. Threads of quartz are prac- 

 tically free from elastic fatigue, and are most suitable for the 

 torsion threads of instruments of precision. Quartz can be 

 drawn so fine that the thinnest parts are beyond the power of any 

 possible microscope to define them. Experiments were made, 

 showing the discharge by flame of electrically-spun threads. 



Sir John Fowler and Mr. B. Baker exhibited a series of most 

 marvellous photographs of the 1700-feet span cantilever bridge 

 now in course of construction across the Firth of Forth. Some 

 of these photographs will be exhibited to-morrow at the Royal 

 Institution. Specimens of wire and other articles made from 

 " platinoid," manufactured by Mr. F. W. Martino, v/ere exhibited 

 by the London Electric Wire Company. Platinoid is untarnish- 

 able under atmospheric influences, and is specially suited to be a 

 substitute for platinum-silver, German silver, &c., for electrical 

 purposes, ashy experiments it has proved itself unchanged under 

 variation of temperature (see Proceedings of the Royal Society, 

 No. 237, 1885). Major H. S. Watkin exhibited a Watkin patent 

 aneroid invented by himself, and manufactured by Mr. J, J. 

 Hicks. It is well known that aneroids have been made of all 

 sizes, from 3 feet to half an inch in diameter ; the length of the divi- 

 sions on the scale representing inches on the mercurial barometer 

 have also been varied to suit different purposes ; but inasmuch 

 as there was only one circle of figures, either the number of inches, 

 and therefore the extreme height at which the instrument was 

 available, had to be restricted, or the dimensions of the scale 

 contracted in order to obtain a longer range. Major Watkin's 

 patent index gets over this difficulty, and an open scale can now 

 be obtained, combined with great length of range. Thus, m 

 the 4-inch patent aneroid i inch on the mercurial barometer can 

 be made to represent from 4 to 10 inches, and yet be available 

 for great heights. 



