July 5, 191 7] 



NATURE 



;75 



The Board of Agriculture and Fisheries announces 

 the publication of a second edition of vol. iv. of the 

 special reports on the mineral resources of Great 

 Britain, which have been prepared by the director of 

 the Geological Survey in response ^ numerous in- 

 quiries that have arisen through the conditions brought 

 about by the war. In the main it is a reprint of 

 the first edition, wherein the properties, sources, and 

 uses of fluorspar, and details of all workings in 

 Britain, active and inactive, are given. 



OUR ASTRONOMICAL COLUMN. 



Comet 1916b (Wolf). — The following ephemeris for 

 Greenwich midnight is given by Messrs. Crawford and 

 Alter in Lick Observatorj- Bulletin No. 295. It is 

 based upon revised elements, calculated from observa- 

 tions made by Barnard on 1916 April 24, 1916 Decem- 

 ber 31, and 1917 April 21 : — 



Decl. Log ii 



1917 



Julv 6 



8 



10 



12 



14 

 16 

 18 



20 

 22 



24 

 26 



28 



30 

 Aus. I 



RA. Decl. Log A Bright- 



h. m. s. , , // ness 



22 57 3 24 40 7 00496 



23 o 15 40 13 00461 2-48 

 3 21 38 31 00426 



6 19 34 58 00391 2-53 



9 II 29 32 00357 



II 55 22 10 00324 257 



14 32 12 50 00291 



17 I 24 I 30 0-0259 2-6l 



19 2T, 23 48 8 00228 



21 37 32 43 00198 264 



23 43 23 15 13 00168 



25 41 22 55 39 00140 267 



27 31 33 59 001 14 



23 29 14 22 10 13 00088 2-68 



R.A. 

 h. m. 



1917 



July 4 9 40 50 



8 42 51 



12 44 46 



16 46 35 



20 48 21 



-4 50 3 



28 9 51 45 



Decl. 



Log -\ 



+ 10 55 o 2357 



9 59 02659 



9 8 02929 



8 22 0-3171 



7 40 0-3389 



7 o 0-3585 



+ 6 23 0-3762 



The ephemeris is for Greenwich midnight Uourn. 

 recedmg from the earth. - 



NO. 2488, VOL. 99] 



The unit of brightness is that on .April 21, 1917, 

 when the comet was observed by Barnard to be not 

 brighter than 12th magnitude. It is quite improbable 

 that the comet will become visible to the naked eve, as 

 was at one time anticipated. 



Co.\iET 1917a (Mellish).— Prof. E. Stromgren sends 

 us the following communication from Copenhagen 

 Observatory :— " Prof. S. S. Hough, director of the 

 Cape Observator\-. writes :— The discovery of a new 

 naked-eye comet by Warren was announced to us by 

 telephone on April 15. From observations made in 

 this observatory on April 18, 20, and 22 the following 

 elements of the orbit have been derived : — 



T = 1917 April 10-8043 

 a, = 124° 32-6"j 

 Elements : Q, = 85' 42-9' -For equino.>c of date 

 /= 32^ 6-i'J 

 9 =0-1975 

 "The comet is 1917a (Mellish)." 



Comet 191 76 (Schaum.asse).— The following con- 

 tinued ephemeris for this comet, bv Messrs. Fayet and 

 Schaumasse, is based upon elements calculated from 

 observations made at the Nice Obser\atorv :— 



I-og r Bright 



DfSS 



0069 1 0-3 



00885 0-2 



01073 0-2 



01255 O-I 



OI43I O-I 



O-160I O-I 



01765 O-I 



Rotation i.n Plaxetarv Nebllje. — In continuation 

 of their previous investigations (N.\ture, vol. xcvii., 

 p. 268), Prof. W. W. Campbell and Mr. W. H. Moore 

 have announced that the planetary nebula N.G.C. 7662 

 shows rotational effects very definitely in its spectrum, 

 and that the bright nebular lines are doubled in the 

 parts corresponding to the central region of the nebula. 

 The most satisfactory interpretation is considered to 

 be that the lines are widened by the differential radial 

 velocities in the central part ,of the nebula, and that 

 an outer stratum of absorbing nebulosity-, with a 

 slower rotation, is responsible for an absorption line 

 lying nearly centrally along each bright line {Popular 

 Astronomy, vol. xxv., p. 313). The nebula N.G.C- 

 7026, the general outline of which is a relatively flat 

 ellipse, is also rotating rapidly, and the evidence is 

 fairly conclusive that there is an outer equatorial zone 

 of absorbing matter. A further example of high 

 angular speed of rotation has been found in the 

 nebula Jonckheere 320. 



THE USE OF ZIRCON I A AS A 

 REFRACTORY MATERLiL. 



THE Transactions of the Ceramic Society, vol. xvi., 

 part i., contain an interesting article by Mr. 

 J. A. Audley on the above title. This substance, ZrO,, 

 occurs somewhat widely distributed, chiefly in the 

 form of the mineral zircon, in which it is combined 

 with silica. A more abundant source has recently been 

 found in the mineral Baddeleyite, which contains from 

 about 80 to 94. and even 98, per cent, of zirconia. This 

 mineral was discovered in 1892 almost simultaneously 

 by Hussak in southern Brazil and by L. Fletcher in 

 Ceylon, the former deposit being much the more ex- 

 tensive and valuable. It also occurs in North America, 

 Australia, and the Ural Mountains. Zirconia is also 

 a by-product of monazite sands. Baddeleyite has a 

 hardness of 6-5 and a specific gravity of 4-4 to 6. It 

 is insoluble in acids, except hydrofluoric acid, but is 

 easily attacked by fused potassium hydrogen sulphate. 

 The melting point of raw zirconia is in the neigh- 

 bourhood of 2000° C, that of the purified material 

 being considerably higher. It can be both melted and 

 volatilised in the electric furnace. It is a " neutral " 

 substance of the same type as alumina and is said to 

 have a high resistance to the fluxing action of both 

 acid and basic slags. Its heat conductivit}' is remark- 

 ably low, and its coefficient of expansion on heating is 

 nearly as low as that of quartz glass, both of which 

 are very valuable properties. It resists the action of 

 fused cyanides and alkalies. 



Dr. J. A. Harker was one of the first in this country 

 to direct attention to the valuable properties of zir- 

 conia, but the matter has only recently been taken up 

 for investigation, and much more attention has been 

 paid to it abroad, particularly in , Germany, where 

 numerous patents have been taken out. It was 

 applied to the manufacture of muffles, retorts, and 

 tubes by Pyfahl in 1904, and two years later by the 

 Heraeus Company for crucibles in which quartz was 

 to be fused. The suggestion has also been made to 

 replace thoria or yttria as an inner coating for the 

 iridium tulje in the Heraeus iridium furnace. 



As a lining for electric arc furnaces the natural product 

 is good enough, its high melting point, low thermal con- 

 ductivity, and small coefficient of expansion making it 

 particularly suitable for this purpose. Now that it is 

 obtainable at comparatively reasonable prices, it can 

 be used for the manufacture of refractorv bricks. The 

 market price in Germany before the war varied from 

 31L per metric ton for the crude mineral to 50Z. for 

 the 98 per cent, variety. It has been found that a 

 zirconia-Iined hearth of an open-hearth steel-making- 



