iS4 



NA TURE 



[June 21, 1894 



chemical properties expeclerf of free fluoiine. The compound 

 now described is a fluorplumbale of the composition 3KF. IIF. 

 PbF,. It may be obtained by three methods. The fir^-l 

 consisis in treating the freshly precipitated hydrated oxide of 

 lead, PbjO- . 3H,0, a substance described by Dr. Branner in 

 the year 1SS5, with a mixture of hydrogen potissium fluoride 

 and hydrotluoric acid. The lluorplumbate is separated from 

 the lead difluoride simultaneously formed by crystallisation from 

 hydrofluoric acid. The second method consists in substituting 

 fluorine for oxygen in the plumbates of Fremy. Peroxide of 

 lead and caustic potash, in the propottions of the compound 

 3KOII . PbO;, are fused in a silver crucible ; the product is 

 moistened with water, and then added gradually to excess of 

 pure hydrofluoric acid. The filtered solution is evaporated to 

 the crystallising point in a current of air, and as soon as crystals 

 commtnce to form is placed in a vacuum desiccator. Crystals 

 of the salt are then depreited. The third method cmsisls in 

 displacing the acetic acid in lead telracetate by fluorine. One 

 molecular equivalent of lead telracetate is added 10 three 

 equivalents of hydrogen potassium fluoride, HF . KF, dissolved 

 in hydrofluoric acid ; crystals of potassium fluorplumbate are 

 formed upon evaporation, either in the air or in vjciio. 

 Analjses of the crystals prepared by all three methods indicate 

 the composition 3KF . IIF . PbF^. 



The needle-shaped crystals, which frequently attain the 

 length of a centimetre, and ate grouped radially, have been 

 found to be in all probability monoclinic in symmetry, and 

 ismorphous with the analogous fluorstannate described by 

 Marignac. 



Potassium fluorplumate is permanent in dry air, but becomes 

 brown in moist air, being decomposed by water, with formation 

 of hydrated peroxide of lead, hydrogen potassium fluoride, 

 and free hydrofluoric acid The effect of heat upon the salt is 

 most interesting and important. The experiments should be 

 carried out in a platinum tube. .-\t ioo°-ilo' the crystals 

 remain unaltered. .\t 200 hydrogen fluoride commences to 

 be evolved in small quantity. When subjected to a much 

 higher temperature, after previous heating for several hours 

 at 230°-25o', a gis commences to be evolved endowed with the 

 odour ascribed by Moissan to fluorine. This occurs much 

 below a red heat. The gas liberates iodine in such large 

 quantities from iodised starch paper as to cause it to be de- 

 posited in crystals, and small crystals of silicon held in the open 

 end of the lube not only burn with a vivid incandescence, but 

 even with explosive violence. There can, therefore, be no 

 question that the gas is free fluorine, and it would thus appear 

 that Dr. Brauner has discovered a trustworthy purely chemical 

 process of isolating the element . Potassium fluorplumbate 

 io^es its hydrogen fliiride almost completely at 230°, without 

 losing more than a trace of fluorine from the lead tetrafluoridc. 

 Any small traces of hydrogen fluoride subsequently evolved 

 along with the fluorine at the higher temperature may be 

 readily removed by Moissan's method of passing the gas over 

 potassium fluoride. 



Dr. Braanerhas already obtained evidence of the existence 

 of a whole series of fluorplumbate', analogous to Marignac's 

 fluorstannates, and is now engaged in studying the sodium salt. 



A. E. TUTTON. 



A SURVEY OF THE ENGLISH LAKES. 



AT the la?t meeting of the Royal Geographical Society a 

 ■^ paper was read by I)r. Hugh Robert Mill, on the Lake 

 District of Northwestern England, of which the following is 

 an abstract :— The lake district is a remarkably definite and 

 symmetrical geographical unit. It may be roughly described 

 as a circular mass ol^ elevated land, highest in the centre, and 

 furrowed by a series of valleys running from the centre toward 

 the circumference like the spokes of a wheel. Most of these 

 valleys contain long narrow lakes of considerable size, and of a 

 difTerent type from the small round mountain tarns which also 

 occur in the district. 



An account wa.s given in the paper of the methods employed 

 for ascertaining the depth and fixing the position of each sound- 

 ing, and for mapping the resulting inforiuation. The lakes 

 considercti were Wtndermcrc, Ullswa'.cr, Conislon Water, 

 Wastwatcr, F^^nnerdale Water, liultermcrc and Crummock 

 Water, Derwcntwalcr, Basscnthwaitc Lake, and Ilaweswatcr, 

 each of which was found to have certain special characteristics 

 which distinguished it from all the others. The soundings were 



NO. 1286. VOL. 50] 



carried out by the author, assisted by Mr. E. Heawood, Mr, 

 Shields, and others. 



There are two main types amongst these lakes, the shallow 

 and the deep. The former, including only Derwentwater and 

 Hassenthwaile, are the broadest of all the lakes ; they average 

 tS feet in depth, their mean depth being only 25 per cen'. 

 f the maximum depth, a smaller ratio than for any other lakes. 

 The bed of these lakes may be roughly described as an undulat- 

 ing plain, grooved and ridged into shallow h'>ll'>ws, and low 

 shoals running pirallet to the I'lng axis of the lake. The con- 

 figuralirn suggests that they may have been shallowed by glacial 

 accumulations. 



The second, or deep type, the shallowest of which has an 

 nveragc depth of 40 fee', and in which the average depth varies 

 from 56 to 6t percent, of the maximum depth, comprises all 

 the other lakes except, possibly, Enneidale, which combiues 

 the characteristics of both types. They are long, narrow, some- 

 times winding like Ullswater, or slightly curved in outline like 

 Wastwaler and Haweswater. The most characteristic lie in 

 long narrow valleys with steeply sloping sides, and the slopes 

 are continued under water with almost equd steepness, in some 

 cases with greater steepness, and terminate in a nearly flat floor. 

 The typical form of this class of lake is thus a steep-sided flat- 

 bottomed trough, diversified along the slopes by the still steeper 

 conical mounds of debris thrown down at the mouths of streams. 

 In Mnweswater the largest example of a delta occur-, nearly 

 cutting the lake in two ; while But'eruiere and Crunini'jck, 

 lying in one uniform valley, are entirely separated, proSably by 

 the same action, and Derwentwaler is also divided from Bassen- 

 thwaite by a broad alluvial plain. Although most of the Lakes 

 show only one clearly defined trough, the two largest are divided 

 into distinct basihs. In Windermere, the shoal on which Belle- 

 isle and the other islands ofT Bowness, rise separates the deep 

 and wide upper basin from the less deep and much narrower 

 lower basin. In Ullswater each of the three reaches of the 

 lake contains a definite basin separated from the others by 

 broad or narrow bars. From one of these the island of I louse- 

 holm rises, a mass of strongly glaciated rock ; but while the 

 position of the basin to the south of it seems to confirm the 

 glacial theory of the excavation of the hollow, the hollow to the 

 north of the island is so situated as to make its origin by glacia- 

 tion somewhat dilTicult to understand. 



Three of the lakes have depths which descend below sea- 

 level. In W.astwater 217 acres lie beneath sea-level, so that if 

 drained to that extent it would present the appearance of a lake 

 still 5S feet in depth at one point. Windermere, if similarly 

 drained, would show a northern lake 3i miles long with a 

 maximum depth of 90 feet, and 3 miles further south a narrower 

 lake I mile in length and only 14 feet deep at itsdeepe^t, while 

 south of this there would be a still shallower lagoon half a mile 

 long. In Collision reduced to sealevel there would probably 

 appear one narrow lake 2j miles long and 42 feet in maximum 

 depths. All the other lakes are situated at such elevations that 

 they do not approach sealevel in their greatest depths. 



Altogether, the lakes which have been sounded and mapped 

 cover an area of 20 square miles of unexplored territory. Con- 

 toured maps of the ten lake basins under consideration have 

 been supplied to the Ordnance Survey for incorporation on the 

 official maps of the country. 



THE RECENT DISCOVERY OF FOSSIL 

 REMAINS AT LAKE CALABONNA, SOUTH 



I AUSTRALIA.' 



I. 

 ■pROM time to time notices have appeared of a remark- 

 ^ able discovery of fossil bones at Lake Mulligan in the 

 interior of South .Vustralia, but so far there has been no connected 

 statement of what has been done in the way of developing the 

 discovery. For reasons which will be evident, it is not yet 

 I ossible to announce the results with anything more than a 



I rough approximation, which leaves many interesting cjueslions 

 unsolved, or even untouched. Still, in view of its pakxon- 

 tological importance, it seems desirable that any available 



' information should be given without further delay. 



Necessarily a fragmentary and imperfect record, I trust the 



I following account will, at least, aflbrd evidence th.at the 



1 authorities of the South .Vustraliaii Museum are fully alive to 



the interest of the issues involved, and that, so far as their not 



1 ny Dr. E. C. Slirlinn. F.R.S., CMd , Hon. Director, South Auslraliai) 



{ Museum. 



