May 26, 1887] 



NATURE 



91 



Meteor-Showers. 



R.A. Decl. 



Near y3 Coronae . 



From Vulpecula 

 Near j Pegasi 



227 

 290 

 303 

 333 



30 N. 



60 N. Rather slow. 



24 N. Swift. 



27 N. Very swift. 



GEOGRAPHICAL NOTES. 



Prof. Guido Cora has constructed a map of the district 

 around Massowah on a scale of i : 200,000. He has been 

 able to make use of a variety of original material, and the 

 map will be of use to those interested in the events which are 

 taking place in that region. 



The May number oi Petcnnann begins with a short paper on 

 the ethnology of British Columbia, by Dr. Fr. Boas (with map). 

 Dr. H. Polaliowsky contributes a paper on the proposed 

 Nicaragua Canal from Grey town to Lake Nicaragua ; Paul 

 Emmrich, a paper on the Transvaal gold-fields ; and Dr. 

 Rink, on recent Danish exploration in Greenland. Herr Wich- 

 mann gives an abstract report of the proceedings of the Ge.man 

 Geographentag at Karl>ruhe. 



The new number (Band v. Heft 2) of the Mittheilungen of 

 the German African Society contains the results of several recent 

 important African expeditions. There is a large-scale map and 

 sections by R. Kiepert, of Bohm and Reichard's journey from 

 Lake Tanganyika to the Lualaba, with remarks by Herr 

 Reichard, observations on altitude, and on the meteorology of 

 the region, by Danckelman. We have also a map of Standinger 

 and Hartert's journey to Kano, Sokoto, and Gandu, with their 

 journals, and remarks on the hypsometrical observations by 

 Danckelman. Prof. Zoppritz contributes a paper on the late 

 Herr Flegel's thermo-barometrical observations on the Niger. 

 There is a letter fro n Lieut. Tappenbeck on his Congo explora- 

 tion of 1885, and an analysis of Lieut. Kund's boiling-point 

 observations by Danckelman. 



ON ZIRCONS AND OTHER MINERALS 

 CONTAINED IN SAND. 



/^WING to recent attempts to employ the brilliant light of 

 ^"^ incandescent zirconia and allied earths instead of that of 

 gas or electricity, attention has been drawn to the sources of the 

 rarer earths. 



It occurred to me that an inexhaustible supply might be 

 obtained from the small crystals of zircon so widely distributed 

 in rocks, sands, and soils, if an easy method of concentration 

 could be found. I wished particularly to examine some of the 

 larger deposits of sand, especially the fine-grained deposits, 

 but was stopped by want of the requisite appliances. The 

 matter having been mentioned by a friend to the Director- 

 Cieneral of the Geological Survey, I at once received permission 

 10 use, for this investigation, the petrological laboratory attached 

 to the Survey. The following results were obtained therein. 



The denser minerals were separated from the sand by means 

 of Sonstadt's solution of density 2 "86, and borotungstate of 

 cadmium of the density of 3 '2. 



Per cent. 



Dense minerals in Lower Bagshot sand, Hampstead 3-85 



,, ,, another sample 360 



,, ,, another sample from appar- 



ently a different deposit 

 near the Fire-engine Office 1*04 



,1 ,, High Beeches, Essex i'32 



,, Glacial drift sand, Bagillt, North Wales 0-30 



,, Casting sand, BuUwell, near Nottingham o'i6 



,> Lower Pagshot sand, near Otterbume, Hants ... o'i2 



These heavy minerals were found to be composed principally 

 of matter attracted by a strong magnet, and of zircons, rutiles, 

 tourmalines, and other grains, the relative proportions varying 

 considerably. It will be observed that the richest and the 

 poorest samples were from deposits of the Lower Bagshot sands. 

 The drift sand from North Wales contained, in addition, many 

 garnets. [Since this was written I have received a sample from 

 High Beech Reservoir, 359 feet above Ordnance datum, con- 

 taining 4 per cent, of dense minerals.] 



The sand to which I devoted most attention, and of which I 

 propose to give an account, is represented in the foregoing table 



by the first two samples. The samples were taken by me from 

 a cutting recently made for the construction of a drain to con- 

 nect " The Spaniards " and North- End, Hampstead. It was 

 2 or 3 feet wide, and ro or 12 feet deep through great part of 

 its length. It passed through a fine-grained yellowish sand, 

 which was thrown out of the cutting or tunneled through in 

 order to lay the drain-pipes. I made an average sample with 

 as much care as though the sand had been a valuable ore which 

 I was sampling for sale or purchase. It represented at least 1000 

 tons of sand in sight or cut through, and probably many acres of 

 such sand on either side of the cutting. It consisted of grains 

 so small as to pass almost entirely through a piece of cambric, 

 120 holes per square inch, stretched on a frame and used as a 

 sieve. The average size of the grains was about the two- 

 hundreth of an inch. 



By means of dense solutions, vanning, analysis, and the con- 

 stant use of the microscope, it was found that the sand had the 

 following composition. It is given as an approximation to the 

 truth, and does not, I think, vary more from it than must be 

 expected in cases where it is not possible to get the minerals 

 pure enough for weighing. Only under the microscope could 

 the mixtures and impurities be estimated. 



Per cent. 

 Quartz, with i or 2 percent, of flint fragments ... about 75 



Feldspar , , 20 



Grains attracted by a strong magnet ,, 2 



Clay ... I 



Zircons in recognisable crystals ,, J 



Grains, more or less opaque, probably zircons ,, \ 



Rutiles „ \ 



Tourmalines ,, -ff, 



In addition to the above, there were about i per cent, of grains 

 over the density of 3 '2, in regard to the composition of which I 

 cannot at present say anything. A few appeared to be cleavage 

 flakes of cyanite, but the majority were opaque earthy-looking 

 bodies of various colours. 



Feldspars. — These were nearly all of density equal to or lower 

 than that of quartz. The majority were more or less cloudy, but 

 some were quite transparent, showing the structure of microcline. 

 A few showed the banded structure of plagioclase. Owing to 

 the small size of the jjarticles, and to their cavities and inclosures, 

 I found it impracticable to get a satisfactory separation by dense 

 solutions ; and as it was impossible to distinguish the grains in 

 all cases under the microscope, recourse was had to analysis of 

 grains (consisting principally of quartz and feldspar) floated off 

 from the denser minerals in a solution in which quartz floated 

 and anorthite sank. It was found that they contained 94 per 

 cent, of silica and 4"6 of alumina, with an unweighable trace of 

 lime. The alkalies were not determined. This would corre- 

 spond to about 20 per cent, of feldspar, but the estimate is perhaps 

 rather high, as amongst the matter floated by the solution were . 

 found some particles which looked like glauconite covered by a 

 transparent covering of varying thickness ; also a little mica 

 and some opaque grains of doubtful origin. It was interest- 

 ing to note how the small fragments of feldspar have remained 

 unchanged since the parent rocks were formed, and as they sur- 

 vived the disintegration of those rocks so they have continued 

 unchanged in the sands. I saw several containing each a small 

 zircon, and some contained what I think were microliths of apatite. 

 The feldspars were mostly in angular fragments like the quartz. 



The zircons are generally transparent and colourless prisms 

 with double terminations of various kinds ; many are more or 

 less rounded and some wholly rounded as by attrition. 



The rutiles are oblong and rounded grains, but many are 

 sharply edged prisms, and a few have double terminations. 

 Twins are not common, but both knee-shaped and kite shaped 

 twins occur. These rutiles resemble those of the metamorphic 

 rocks, in which rounded grains and sharply defined crystals are 

 met with side by side. 



The tourmalines are generally in flat plates, more or less 

 rounded, but some are perfect crystals with double terminations. 

 They vary much in colour and power of absorption. Various 

 methods of concentrating the zircons were tried. The simplest 

 found was to sift the sand in air or water through a sieve with 

 120 holes to the inch, that being the smallest mesh I could meet 

 v\ith. In coarse-grained sands, such as the drift sand of North 

 Wales, a considerable enrichment is thereby at once eftected, 

 but only a partial enrichment takes place in working with sands 

 so small-grained as to pass entirely through the sieve. 



Thus when 8 ounces of the Hampstead sand were sifted till 

 4 ounces had passed, it was found that the zircons and rutiles, 

 being smaller, smoother, and heavier than the sand, passed 



