S2 



NATURE 



[November 25, 1897 



feet. In accord with the peat-Uke alluvium out of 

 which they are excavated and constructed, their colour is 

 a dark ashen grey or nearly black. A distinctive feature 

 ■of these meridian ants' nests is their highly ornate archi- 

 tectural style. They consist of a congeries of slender 

 pinnacles erected close to one another in the same 

 straight line, and which are finally amalgamated. Upon 

 these primary pinnacles numerous subsidiary ones are 

 usually constructed. The completed edifice, with its full 

 •complement of spires and pinnacles, comes thus when 

 viewed end on, as shown in certain of the photographs 

 taken, to present in miniature a by no means remote re- 

 semblance to the architectural pile of some grand 

 cathedral. 



A second and simpler form of meridian ants' nest is 

 especially abundant a few miles inland from Port Darwin. 

 It differs from the preceding type in its more massive 

 and less ornate structural plan. The upper edge is 

 inearly smooth or irregularly serrated, but not produced 

 into a series of slender pinnacles. It is further note- 

 worthy, that the environments pertaining to these two 

 meridian varieties differ materially. With the Port 

 Darwin type the habitat affected is that of open grassy 

 plains, while in the Laura Valley form the nest mounds 

 are most abundantly constructed in typical, though 

 thinly wooded forest land. 



The raison detre of the north and south directions of 

 the longer axial planes, so eminently characteristic of the 

 so-called " Meridian " ants' nests, has given rise to much 

 speculation and a variety of interpretations. By some it 

 is supposed to bear a direct relationship to the prevailing 

 winds. As, however, those in the districts where these 

 ant-hills occur are chiefly south-east or north-west, ac- 

 cording to the seasonal monsoon, that interpretation can- 

 not be accepted as satisfactory. To the writer's mind a 

 more probable explanation would appear to present itself 

 in connection with the circumstance that being con- 

 structed in this precise meridian line, their larger surface 

 presents the least possibly prolonged exposure to the 

 meridianal rays of the tropical sun, and that the 

 structures are consequently so built that they shall 

 absorb and retain a minimum amount of solar heat. 

 This question is, however, an interesting one that un- 

 doubtedly invites further scientific investigation. The 

 subject of Australian termitaria constitutes, it may be 

 noted, a copiously illustrated chapter in the writer's 

 recently published work, " The Naturalist in Australia." 



W. Saville-Kent. 



THE LIQUEFACTION OF FLUORINE. 



"P LUORINE was prepared for the first time in 1886 by 

 -*■ Prof. Moissan, as a product of the electrolysis of 

 anhydrous hydrogen fluoride contained in a platinum ap- 

 paratus provided with fluorspar stoppers; the new gas was 

 at once found to be the most active chemical substance 

 known, many elements and organic compounds, such as 

 arsenic, antimony, sulphur, iodine, alcohol, and turpen- 

 tine, immediately and spontaneously bursting into flame 

 when plunged into an atmosphere of fluorine. On mixing 

 the gas with hydrogen, even in the dark, a violent de- 

 tonation immediately occurs, hydrogen fluoride being 

 produced. The violent action of fluorine upon nearly all 

 substances with which it is brought into contact, obviously 

 renders extremely difficult all experimental work involving 

 the use of the free element. The great manipulative diffi- 

 culties necessarily arising whilst dealing with the gas on 

 the large scale have, however, been very happily sur- 

 mounted by Prof. Moissan and Prof. Dewar, who re- 

 cently described to the Chemical Society the method by 

 which they have succeeded in liquefying fluorine, and de- 

 termining the more important properties of the liquid 

 substance {Proc. Chem. 5f^., November 4, 1897, p. 175). 

 It seemed likely that the great chemical activity of 



NO. 1465. VOL. 57] 



fluorine might so far decrease at low temperatures as to 

 allow of the manipulation of the material in a glass vessel 

 cooled in liquid air ; this was found to be the case. 



The fluorine required in the work was prepared by the 

 electrolysis of anhydrous hydrogen fluoride ; this liquid 

 being a non-conductor, was made a conductor by dis- 

 solving in it potassium fluoride. The liberated fluorine 

 was freed from hydrogen fluoride by being passed first 

 through a platinum worm immersed in a cooling mixture 

 of solid carbon dioxide and alcohol, and subsequently 

 through platinum tubes containing dry sodium fluoride. 

 The purified gas was then passed down a vertical 

 platinum tube fused to the neck of a thin glass bulb 

 which served as the collector, and an exit was provided 

 through a narrower platinum tube contained inside the 

 first. On cooling the apparatus down to - 183° in boil- 

 ing oxygen whilst the fluorine is passing through, no 

 liquefaction occurs, but on reducing the pressure under 

 which the oxygen is boiling, and so lowering the temper- 

 ature to - 185°, the fluorine condenses in the glass bulb 

 to a very mobile yellow liquid ; on removing the bulb 

 from the cooling bath the liquid fluorine boils vigorously. 

 Other experiments made with boiling liquid oxygen and 

 liquid air as refrigerating agents indicated that fluorine 

 boils at about - 187°, namely at the boiling point of 

 liquid argon ; from this the probable critical temperature 

 and pressure of fluorine are deduced as - 120" and 40 

 atmospheres respectively. 



At these low temperatures fluorine is without action 

 on glass, and does not displace iodine from iodides ; 

 silicon, boron, carbon, sulphur, phosphorus and reduced 

 iron, all of which spontaneously ignite when brought 

 into contact with fluorine at ordinary temperatures, do 

 not inflame if, after being cooled in liquid oxygen, they 

 are plunged into an atmosphere of fluorine. Hydrogen 

 gas inflames spontaneously, with considerable evolution 

 of light and heat, when directed on to the surface of 

 liquid fluorine at - 190^ ; on passing fluorine on to 

 solidified turpentine cooled by boiling liquid air, a series 

 of explosions occurred resulting in the destruction of the 

 apparatus. It thus seems that the great affinity existing 

 between hydrogen and fluorine is not overcome at 

 - 190". A little liquid fluorine falling on the floor 

 instantly inflames the wood. Fluorine is soluble in 

 liquid oxygen, and on passing in the gas a white 

 flocculent precipitate is formed which, after filtering 

 off, deflagrates violently as the temperature rises ; it 

 is possibly a hydrate of fluorine. 



Determinations made by floating pieces of various 

 substances in liquid fluorine indicate that its density 

 is about 1*14, and from the invisibility of amber im- 

 mersed in the liquid the refractive index of the latter 

 would seem to be higher than that of liquid air or 

 oxygen. Liquid fluorine shows no magnetic phenomena 

 when placed between the poles of a powerful electro- 

 magnet ; it has a smaller capillarity constant than liquid 

 oxygen, and does not solidify at - 210^ It has no 

 absorption spectrum, and its colour is the same as that 

 of the gaseous element. W. J. P. 



THE LEONID DISPLAY, 1897. 



VERY unfavourable weather appears to have pre- 

 vented the successful observation of the Leonids 

 at their recent return. In consequence of this the 

 impression seems to have gained ground that the 

 phenomenon did not occur as predicted. This is, how- 

 ever, a mistake. Could those observers who saw so 

 little on the night of the 13th, have viewed the sky late 

 on the following night, they must have been satisfied 

 at the character- of the display. Between about 4.30 

 and 6 a.m. on Monday morning the 15th, the usual 

 streak-leaving meteors from Leo became very numerous, 

 and some of them were unusually brilliant, one, which 



