March 23, 191 1] 



NATURE 



12 



duii' s under great difticuiiies, and without the status, the 

 aurhoritv, or the salary of a Government astronomer. 

 The Public Service Board recommended the removal of 

 the observatory to a more suitable locality, on an eminence 

 not too far from the capital ; the appointment of an 

 astronomer with high scientific attainments at a suitable 

 salary (8ooZ. per annum and a residence) ; the re-equipment 

 with modern instruments, including a large telescope of 

 not less than 15 inches diameter ; and that steps be taken 

 to affiliate the observatory and the university. Whilst the 

 latter recommendation has given rise to some difference of 

 opinion, there is no dissension on the question of the 

 necessity and advisability of re-establishing the observatory 

 on a proper basis, so that New South Wales shall not be 

 behind other States and countries in the prosecution of 

 astronomical research. But the minds of the Ministers 

 responsible are occupied with " important " matters ! 



The Spectra of Spiral Nebula and Globular Star 

 Clusters.— On May 20, 1909 (vol. Ixxx., p. 354) we 

 directed attention in these columns to some interesting 

 results, obtained by Mr. Path at the Lick Observatory, 

 concerning the probable structure of spiral nebulae and 

 globular clusters as indicated by their several spectra. A 

 second paper by the same author appears in No. i, vol. 

 xxxiii., of T/jc Astrophysical Journal, as a contribution 

 (No. 49) from the Mount Wilson Solar Observatory. 



For this later research Mr. Fath employed a spectro- 

 graph attached to the 60-inch reflector, and obtained 

 spectra that are but little longer than 3 mm. between 

 AA ^700 and 5000; despite their small scale, these spectra 

 afford further^evidence as to the probable structure of the 

 objects under consideration. 



The spectrum of the spiral nebula N.G.C. 650-651 shows 

 seven bright lines, at 373, 387, 397, 434, 4^6, 496, and 

 501 nn, corresponding to lines usually found in the spectra 

 of gaseous nebulae. N.G.C. 4725 gave a spectrum of the 

 sola'r type with lines at F, G, H, and K, and a spectrum 

 of N.G.C. 4736 is similar, with lines at F, G, 425 nfi, 

 410 nfj., H, K, and 387 u/u- It is, however, a curious fact 

 that the last-named spectrum differs considerably from 

 one of the same object secured in the earlier research ; 

 the Mount Hamilton plate gave what was assumed to be 

 a bright band at 406 nn, and absorption lines at 387 and 

 400 MM, but as it was not in good focus other plates will 

 be taken with a new specially designed spectrograph 

 which, it is hoped, will be constructed shortly. 



Whilst recognising that the evidence is, as yet, slight, 

 Mr. Fath suggests that these results point to a progressive 

 change in the spectra of nebulae with change of form. 

 Starting with irregular nebulae, like that in Orion, giving 

 bright-line spectra, we pass to probable spiral nebulae such 

 as N.G.C. 650-1, where the spectrum shows bright lines 

 and little or no continuous background, thence to planetary 

 nebulte, such as N.G.C. 6543, giving the bright lines and 

 considerable continuous spectrum. In the fourth type the 

 spiral form is well developed, e.g. N.G.C. 1068, and the 

 spectrum, while still showing bright lines, has also a 

 strong continuous spectrum, and contains absorption lines. 

 The last type, exemplified by the Andromeda nebula, gives 

 spectra of the solar type, and the nebula has condensed, at 

 least partially, to stars. This progression indicates star- 

 clusters as the final product. 



The spectra of eight globular clusters arc _ almost 

 identical, of approximately the F type, in which the 

 hvdrogen series predominates, but, where the spectrum 

 extends far enough, H and K are also found ; a line, or 

 band, near 419 fifi is also a common feature. In the 

 Mount Hamilton plates, the Hercules cluster, N.G.C. 

 6205, gave evidence of the inclusion of more than one type 

 of spectrum, but the more recent work does not support 

 this ; more plates with the slit crossing different parts of 

 the cluster must be obtained. 



The Dark Borders of the Martian Snowcaps.-— In 

 No. 4472 of the Aitronomische Nachrichten, M. Antoniadi 

 reverts to the question of the objective reality of the dark 

 bands which appear to encircle the Martian polar caps. 

 In a previous communication he maintained that, if real, 

 they should show on photographs, but Prof. Lowell and 

 others suggested that the brightness of the caps was so 

 intense that the non-appearance of the dark areas might 

 be accounted for by the photographic halation from the 



NO. 2160, VOL. 86] 



brilliant caps. This suggestion was supported by the 

 statement that the photographs taken in America in 1909. 

 showed the caps to be far more brilliant than the " con- 

 tinents." M. Antoniadi now brings independent testimony 

 countering the statement, and maintains that the dark 

 areas are not obliterated by photographic " spreading." 

 In opposition to M. Jonckheere's contention that the dark 

 bands exhibit the perspective they should do, if real, he 

 states that he has never seen it, and reproduces a draw- 

 ing made by Schiaparelli in 1884 in which the dark band 

 is shown of equal breadth at the middle and at the ends 

 of its major axis. 



Double-star Observations. — Nos. 4479-80 of the 

 Astronoinische Nachrichten contain a large nuinber of 

 double-star observations made by Dr. Doberck at Sutton, 

 Surrey. Most of the observations were made in 19 10, and 

 since 1910-13 the Elizabeth Thompson micrometer has been 

 employed. In determining the scale value, corrections 

 have been applied for aberration, refraction, and proper 

 motion, and the final value obtained is 19-342" ±0-002". 



No. 6, vol. iv., of the Journal of the Royal Astronomical 

 Society of Canada contains a number of double-star 

 measures made by Mr. Motherwell with the 15-inch re- 

 fractor of the Dominion Observatory. The work was com- 

 menced in 1907, the programme being to measure such 

 pairs in Burnham's General Catalogue as are otherwise 

 neglected or of which the motion seems uncertain. 



The " .Axuario " of the Madrid Observatory. — The 

 annual almanac published by the Madrid Observatory con- 

 tains the usual tables and ephemerides for the sun, moon, 

 and planets, and a number of extra tables, in which in- 

 formation as to the aspect of the sky, the azimuth of the 

 pole star, and the passages of certain stars, &c., at given 

 hours, is incorporated. Extensive tables for the calcula- 

 tion of latitude from observations of the pole star are also 

 given, and the volume (191 1) concludes with records of the 

 solar and meteorological observations made during 1909. 



THE NATIONAL PHYSICAL LABORATORY 



DURING 1910. 

 'X'HE General Board of the National Physical Laboratory 

 held its annual meeting at the laboratory on Friday 

 last, March 17, when the report of the executive com- 

 mittee for the year 1910 was formally presented. As 

 usual, a large number of visitors were invited, and were 

 received by Sir Archibald Geikie, president of the Royal 

 Society and chairman of the General Board of the labora- 

 tory, and by Lord Rayleigh, the chairman of the executive 

 committee. 



The reception this 3'ear took place in the buildings of 

 the National Experimental Tank, where the equipment for 

 the experiments to be undertaken on models of ships is 

 now almost complete. The models, 20 feet in length, are 

 cast in clay moulds, and shaped to the correct form by a 

 special machine, which cuts in them a series of horizontal 

 grooves, the operator guiding a tracing point over a corre- 

 sponding sectional drawing. The wax is then trimmed' 

 down by hand to a smooth surface, leaving only the finest 

 trace of the grooves as a guarantee of accuracy. The 

 model is finally measured up on a special measuring table. 



The carriage by which the model is towed along the 

 tank weighs some 15 tons, and is driven by four motors 

 designed to enable a speed of 17 miles an hour to be 

 reached for the steady portion of the run. As is well 

 known, the " model " law requires that the speed shall 

 be proportional to the square root of the linear dimensions, 

 and the speed indicated is therefore more than sufficient 

 for the purposes of the tests. 



The first report of the advisory committee for the tank 

 appears in the report of the laboratory for the year 19 10, 

 ana gives some interesting details of the construction, and, 

 in an appendix, of the movements of the walls due to fill- 

 ing. A more complete account of the tank and its equip- 

 ment, bv the superintendent, Mr. G. S. Baker, will be 

 presented to the Institution of Naval Architects at their 

 meeting next month. 



The visitors to the laboratory were also able to see the 



progress which has been made with the new buildings for 



metallurgv, for which the laboratory is indebted to the 



I generosity of Sir Julius Wernher. In these ample accom- 



