March 20, 19 13] 



NATURE 



OUR ASTRONOMICAL COLUMN. 



The ioo-in. Reflector at Mount Wilson. — Some 

 years ago the Mount Wilson Observatory ordered from 

 France a ioo-in. diameter mirror, the French foundry 

 being the only one in the world which would under- 

 take the casting of such a large mass of glass. The 

 mirror, when delivered in California, was found not 

 to be up to the standard of contract quality, and the 

 French firm undertook to set about casting a new 

 one. In the meantime, as an experiment, it was 

 decided to figure the disc, and Prof. Ritchey worked 

 away at it in the workshop at Pasadena. On the 

 completion of his task, it appears from a note in The 

 Observatory (March) that the tests have shown that 

 the mirror is practically useless. It will be some time 

 before the more perfect disc is procured, but it is 

 hoped that the second attempt will be quite successful. 



Solar Radiation during the Eclipse of April 17, 

 1912. — In the form of an extract from the Comptes 

 fendus de la Society Scientifique, of Warsaw, we have 

 received a paper in which Dr. W. Gorcynski describes 

 the observations of the insolation made at Warsaw 

 during the partial eclipse of the sun which occurred 

 on April 17, 1912. The diminution of the solar radia- 

 tion readings began about half an hour before the 

 eclipse, and remained below the normal for the date 

 for nearly the same time after. The maximum re- 

 duction of the solar radiation attained Sg per cent, at 

 Warsaw, where o-88 of the disc was covered at maxi- 

 mum phase, and the radiation curve agrees fairly well 

 with the phase curve. Between noon and 4 p.m. each 

 sq. cm. of surface received no great calories, at 

 normal incidence, less than usual, and the drop in 

 temperature, as recorded in the screen, was between 

 2 and 3 C. 



Bantu Star Names. — No. 12, vol. xii., of Man 

 contains an interesting article by Miss A. Werner 

 discussing the names by which the stars are described 

 in Bantu by the tribes of Nyasaland. Miss Werner's 

 general impression is that nearly, if not quite, all the 

 peoples with whom she has come into contact have 

 lost much star knowledge which they once possessed. 

 The name for the Pleiades is always etymologically 

 connected with agriculture, being derived from a root, 

 lima, meaning " to cultivate," thus indicating that the 

 Zulus, Swahilis, &c, have employed this asterism, as 

 have so many other primitive races, as a substitute 

 for the modern calendar. The "belt" stars of Orion 

 seem always to be connected with hunting, and the 

 name for Venus conveys generally the idea the planet 

 is the moon's wife. The names applied to Jupiter 

 also suggest a connection with hunting, a native 

 explanation being that a hunting expedition should 

 start on a night when Jupiter is overhead just before 

 dawn. Several other of the names given are of special 

 interest, and tend to show that the astronomical ob- 

 servations of primitive races are essentially utilitarian 

 in character. 



The Explosion of Worlds. — Some interesting 

 speculations as to the possibility of such a world as 

 the earth being shattered by the explosive energy of 

 the now pent-up internal forces are published by Mr. 

 Hudson Maxim in the February number of The Fort- 

 nightly Review. Among other things, he shows that 

 the pressure of the earth's crust is so great that the 

 most powerful explosive known, in any quantity, 

 would fail to do more than shake it locally. Gravita- 

 tional pressure is so enormous that were two solid 

 steel balls, as large as the earth and as hard as the 

 Harveyised surface of armour-plate, gentlv placed in 

 contact they would flow together like water, and 

 could have no variation from a true sphere greater 

 than fifty miles high. By such arguments Mr. Maxim 

 demonstrates the enormous strength and rigiditv of 

 no. 2264, VOL - 9 1 ] 



the terrestrial sphere, and shows that it is immune 

 from the effects of any shattering force less than thtr 

 collision of the solar system with another celestial 

 system. 



The Detroit Observatory. — The first issue of the 

 Publications of the Astronomical Observatorv of the 

 University of Michigan (vol. i., pp. 1-72) contains, 

 inter alia, a most interesting account of the observa- 

 tory and its work. The observatory also makes seis- 

 mographic observations, and the records of the earth- 

 quakes recorded from August, 1909, to January, 1912, 

 are given in the present publication. 



THE I.XSTITUTION OF NAVAL 

 ARCHITECTS. 



THE meetings of the Institution of Naval Architects 

 ■*■ opened on Wednesday, March 12, in the rooms 

 of the Royal Society of Arts. During the three days 

 over which the meetings extended, fourteen papers 

 were presented for discussion. The gold medal of the 

 institution for 1912 was presented to Admiral Sir 

 Reginald Custance, and premiums were awarded to 

 Prof. Giimbel and to Mr. A. Cannon. The Marquis 

 of Bristol, in his presidential address, referred to the 

 loss the institution had sustained in the death of Sir 

 Wm. White, and hoped that some memorial of a per- 

 manent character would be instituted by the various- 

 societies with which he had been connected, and that 

 such memorial might take a form of practical service 

 to the profession. 



Mr. D. B. Morison gave some interesting data 

 regarding the influence of air pumps on the militarv 

 efficiency of turbine-driven warships. According to 

 the latest cruiser practice, a vacuum of 28-5 in. is 

 required at full power in sea water at 55 F. If, 

 under conditions of maximum and constant genera- 

 tion of steam in the boilers, the vacuum falls from 

 285 to 27-5 in., then the loss in power is about 6 per 

 cent. The minimum capacity of an air pump is 

 determined by the quantity of air in the feed water 

 as it enters the boiler, without provision for insidious 

 leakage. From his experience with high-vacuum 

 plants of the highest class, Mr. Morison does not 

 believe that ideal air-tightness can be maintained 

 under the severe conditions of war ; hence the neces- 

 sity for the provision of an air margin in the capacity 

 of the air pumps. Various types of air pumps are 

 discussed in the paper. 



Sir Charles A. Parsons states in his paper on 

 mechanical gearing that such gearing for reducing the 

 speed between the turbine and the propeller is now 

 well advanced beyond the experimental stage. This 

 type of gearing is now in service on vessels repre- 

 senting a total of 26,000 h.p., and there are others 

 under construction aggregating 120,000 h.p., includ- 

 ing two installations of more than 20,000 h.p. each. 

 The Channel steamers Normannia and Hantonia con- 

 tinue to show an economy, as compared with other 

 turbine steamers of somewhat different design on the 

 same service, of about 40 per cent. The Normannia's 

 rearing, inspected recently, shows no signs of wear. 

 Comparative coal consumption trials have been carried 

 out on a cargo steamer, built for the Cairn Line, and 

 fitted with turbines and mechanical gearing, and on 

 a sister ship, the Cairngowan, with exactly similar 

 boilers and propeller, but with triple- expansion 

 engines. The coal was of the same quality, and 

 measured in the same way on both ships, and the 

 geared turbine ship has shown a saving of 15 per 

 cent, in the coal consumption. So far, no limit in 

 regard to the surface speed of the teeth in the gearing 

 has been discerned, and there is no evidence of any 

 limit to the power that can be transmitted by 



