November 17, 1892] 



NATURE 



55 



tap. This will prevent the harmless " snap" from the mixture 

 in the small chamber at the joining of the gas tubes. If a disc 

 more than eight feet be required for the microscope, it will be 

 well to use hydrogen gas instead of ether, since the calibre of 

 the jet cannot in the ether light very well exceed ,'^ of an inch. 



As an extra security, I pack the mixing chamber with asbestos- 

 fibre, moistened with glycerine ; but, as before urged, the oxy- 

 gen must leave the saturator, saturated. 



To insure the coincidence of the foci of the reflector with the 

 optical axis of the microscope, it will be well to place three ad- 

 justing screws in a triangle behind the mirror, and this last may 

 have both a small vertical and horizontal movement. 



I claim for this catoptric arrangement a larger grasp of light 

 than can be got from ordinary lenses, and this may be effected 

 aho ar a small outlay. For the amateur constructor the plan 

 will afford many advantages. G. B. Buckton. 



Note on the Colours of the Alkali Metals. 

 When these metals are heated in a vacuous tube in such a 

 way as to cause an extremely thin sublimate of the metal to 

 condense upon the glass, the film so obtained will be found to 

 possess a beautiful and strongly-marked colour. That this colour 

 is not in any way due to the combination of the metal with any 

 lingering minute traces of oxygen, is evident from the fact that 

 vacuous tubes which have contained the clean and bright metal 

 for years, and in which the metal has been frequently melted 

 and rolled about, and even vapourized in places, and in which, 

 therefore, it is impossible to conceive of any oxygen remaining, 

 will continue to show the phenomenon whenever a portion of 

 the contained metal is heated. The experiment may readily be 

 made by introducing a freshly-cut fragment of the metal into a 

 glass lube sealed at one end and drawn down to a narrow and 

 thickened constriction near the middle. The tube is then drawn 

 out at the open end and connected to a Sprengel pump. As 

 soon as a good vacuum is obtained the tube is warmed through- 

 out its entire length, the pump being still in operation, and the 

 metal heated sufficiently high to cause it to melt and run out of 

 the crust of oxide. When the exhaustion is again as complete 

 as possible the tube is sealed off. The metal is once more 

 melted, the whole tube being at the same time gently heated, 

 and the molten mass allowed to filter through the constriction 

 into the other portion of the tube. The vacuous condition of 

 the tube allows of the metal freely running through an extremely 

 fine aperture, and in this way it becomes perfectly separated from 

 all dross. The tube is then sealed off at the constriction. On 

 gently heating a minute fragment of the bright metal so obtained, 

 by means of a small pointed gas flame, the coloured film of 

 sublimed metal will at once be seen. Viewed by transmitted 

 light, the colour of the film of sodium thus obtained is greenish- 

 blue, inclining to green. Potassium gives a sublimate which is 

 of a magnificent rich purple colour, while rubidium, on the 

 otiier hand, forms a film which is a pure indigo blue. 



In the cases of sodium and potassium, the colour of the metallic 

 sublimates is different from the colour of the vapour as seen when 

 the metals are boiled in an atmosphere of hydrogen. Potassium, 

 it will be remembered, yields under these circumstances a vapour 

 possessing an emerald-green colour, while that of sodium, which 

 appears colourless when seen in small layers, shows a violet or 

 purple colour when viewed through a sufficient thickness. 



When the liquid alloy of sodium and potassium is treated in 

 the same way, the sublimate obtained is found to be greenish in 

 colour nearest to the source of heat, quickly shading off to blue 

 and purple as it is more remote from that point, indicating ap- 

 parently that the two metals sublime separately. 



As a means of observing these colour phenomena, this alloy 

 is more advantageously employed than the solid metals them- 

 selves, for, by rolling the liquid about, the sublimate may be 

 wiped away and the experiment repeated indefinitely in the same 

 tube. 



As to whether the colours of these sublimed films are properties 

 intrinsic to the particular metals, or are merely a function of the 

 physical condition of the substances, it is perhaps rash to 

 dogmatize. A number of other elements have been treated in a 

 similar manner, but without similar results ; thus lithium, 

 cadmium, mercury, arsenic, tellurium, and selenium, when heated 

 in vacuous tubes are readily sublimed, but in no case does the 

 film,^ appear coloured. On the other hand, however, it is well 

 known that some of the very malleable metals when beaten out 

 into thin films are capable of transmitting light varying in colour 

 from g een to violet. G. S. Newth. 



Women and Musical Instruments. 



In answer to Prof. O. T. Mason's letter which appeared in a 

 recent number of Nature (vol. xlvi. p. 561), I may draw atten- 

 tion to the following facts which bear upon a part of the subject 

 which he broaches, namely, the part played by savage women 

 in the use of musical instruments. In the South Pacific the ' ' nose- 

 flute " is very generally, though by no means exclusively, 

 played upon by women. In the account of the voyage of Capts. 

 Cook and King there is in one of the plates a figure of a woman 

 of the Tonga Islands seated under a hut playing upon a " nose- 

 flute." A similar figure of a woman playing upon a " nose-flute " 

 may be seen in plate 28 of Labilladiere s "Voyage de la 

 Perouse" in the representation of a Tongan double-canoe. 

 Melville (" Four Months' Residence in the Marquisas Islands," 

 p. 251) mentions playing upon the "nose-flute" as being '•a 

 favourite recreation with the females." In Wilkes' " U. S. 

 Exploring Expedition," iii. p. 190, there is a description of 

 this instrument as used in the Fiji Islands, and it is stated 

 that "no other instrument but the flute ['nose-flute'] is 

 played by the women as an accompaniment to the voice." 



Turning now to another genus of primitive instiuments, 

 viz., the "musical bow," we find a peculiar local form, the 

 "Pangolo," occurring at Blanche- Bay, New Britain. There 

 are specimens of this at Berlin and Vienna. This instrument 

 is stated by Dr. O. Finsch {Ann. des K. K. Naturhist. 

 Hojmusetims, suppl. vol. iii. pt. i, p. iii) to be only played 

 upon by women of Blanche Bay. Guppy too (" Solomon 

 Islands," p. 142), says that the women of Treasury Island 

 produce a soft kind of music by playing, somewhat after 

 the fashion of a jew's-harp, on a lightly-made fine-stringed bow 

 about 15 inches long. 



It cannot, I believe, be said that any of these instruments 

 have been invented by women, and it is undoubted that 

 women in savagery but seldom figure as performers upon musical 

 instruments. It would certainly be interesting to collect all the 

 instances recorded. I hope that the above few notes regard- 

 ing instruments in the south Pacific may be of use to Prof. 

 Mason, and I can only regret that lack of the necessary 

 time prevents my going further into the matter. 



University Museum, Oxford, Henry Balfour. 



November 7. 



A 



NO. 1203, VOL. 47] 



AN ANCIENT GLACIAL EPOCH IN 



A USTRALIA. 

 VERY interesting "special report" has just been 

 issued by the Department of Mines of Victoria, 

 g:iving an account of the remarkable evidences of glacia- 

 tion observed at a locality about twenty miles south- 

 east of Sandhurst, and about the same distance north of 

 the great Dividing Range.^ The report is illustrated by 

 a map and sections on a large scale, and by eight excel- 

 lent photographic prints, showing the character of the 

 deposit on the surface and in railway cuttings, the 

 striated bed rock, and the striated and grooved blocks 

 and boulders, so that full materials are given for the con- 

 clusion that we have here an undoubted glacial deposit. 

 A brief summary of this report will therefore be interesting 

 to all students of the phenomena and problems of terres- 

 trial glaciation. 



The district now specially described is about fifteen 

 miles in one direction by five in another, and over this 

 area of about thirty-six square miles the conglomerate is 

 continuous, overlying the Silurian rocks of the district. 

 It has generally a rounded or undulating surface, but 

 shows cliffs about ico feet high in some of the gullies, and 

 its maximum thickness is estimated at 300 or 400 feet, 

 while its highest point is about 700 feet above sea-level. 

 As well seen in the cliffs and several railway cuttings, the 

 conglomerate consists of a matrix of sand and clayey 

 matter containing huge boulders, great angular and sub- 

 angular masses of rock, pebbles, and rock-fragments of 

 endless variety of size, form, and material. Many of 

 these masses are planed, scored, striated, or polished. 



' " Notes on the Glacial Conglomerate, Wild Duck Crerk." By E. J. 

 Dunn, F.G.S. (R. .S. Brain, Government Printer, Melbourne, 1893.) 



