June 8, 191 1] 



NATURE 



495 



stable equilibrium, and a third intermediate distance at 

 which they are in unstable equilibrium. As Prof, Pictet's 

 definitions differ so materially from those generally 

 accepted at the present time, and his method of deduction 

 is not very conclusive, or even at times clear, the theoretical 

 portion of his address falls far behind the experimental in 

 point of interest and importance. 



The launch of the Titanic took place at Belfast on 

 May 31, and forms the subject of an illustrated article in 

 The Engineer for June 2, The arrangements for launch- 

 ing were similar to those of the Olympic, and the ship 

 took sixty-two seconds from the first movement until she 

 was afloat. The launching weight was 25,000 tons. The 

 hydraulic rams fitted in order to start the ship were not 

 requisitioned. We understand that the Olympic has com- 

 pleted most satisfactory trials, and has been handed over 

 to her owners a month before her time. 



Engineering for June 2 contains an illustrated descrip- 

 tion of the yacht Progress, fitted with 100 indicated horse- 

 power gas engine and produced and owned by the Empire 

 Oil Engine Syndicate, Ltd., of London. Owing to the cost 

 of oil fuel in many parts of the world, it seems certain 

 that marine internal-combustion engines must be capable 

 of using gas derived from ordinary coal. The engines of 

 this yacht are on the two-cycle double-action principle, 

 driving the propeller direct without the interposition of 

 any gearing. The gas supply is from a suction producer, 

 which has been worked with anthracite, with coke, and 

 with coalite. The patentees are convinced that their 

 accurnulated experience will enable them to supply a pro- 

 ducer capable of working satisfactorily with ordinary 

 steam coal. The engines are so arranged as to secure 

 great ease in manipulation ; as instancing the handiness 

 of the engines, it may be stated that, on coming out of 

 dock on .one occasion, twenty-six different movements were 

 made in the course of twenty-one minutes. The time 

 taken to reverse has been found to be from three to four 

 seconds after the order is given. It is intended to build 

 a second engine to develop from 350 to 400 horse-power, 

 and a corresponding gas plant, in both of which a number 

 of improvements in detail will be embodied. This plant 

 will be fitted on board a vessel of the commercial type. 



A '* GRAPH TEMPLATE," designed by Mr. J. T. Dufton, 

 by means of which standard rectangular hyperbolas and 

 parabolas of large size can be drawn readily on squared 

 paper, has been put upon the market by Messrs. Mac- 

 millan and Co., Ltd. The price of the template in trans- 

 parent celluloid, with instructions, is 6d. net, and in 

 nickel-plated metal 3d. net. 



13 V a printer's error, the inscriptions of the two illustra- 

 tions from " Kearton's Nature Pictures " reproduced in 

 last week's Nature (p. 450) were unfortunately transposed. 



OUR ASTRONOMICAL COLUMN. 



Nova .Saoittarii No. 4. — Circular 164 of the Harvard 

 College Observatory announces the discovery of yet another 

 nova in the constellation Sagittarius. This object was 

 found by Miss Cannon during a rapid comparison of various 

 photographs of the Harvard Map of the Sky on Map 43. 

 It appears on eleven photographs taken between May 22 

 and July 9, 190J, but no trace of it can be found on 148 

 other plates taken in 1892, 3, 5, 6, 7, 8, and 9, and each 

 year from 1900 to 19 10 inclusive; each of these shows 

 the C.D.M. star — 27°i24ii, of magnitude 97, with which 

 the nova at its maximum was equal in photographic 

 magnitude. The exact date of the nova's appearance can- 



NO. 2 171, VOL. 86] 



not be fixed, but the greatest observed brightness was 

 IO-3 on May 22, 1901, and it is not shown on a plate 

 taken on .\pril 10, 1901, although this plate shows a 

 fourteenth-magnitude star 0-3' south of the nova. The 

 fluctuations of brightness appear to be somewhat similar 

 to those of Nova Persei (2). It is of interest to note that 

 seven novas are now known to have appeared in the region 

 covered by Map 43. 



The Mechanical Production ok the Streamers seen 

 IN the Solar Corona. — In order to test the theory that 

 the shapes of observed coronal streams may be accounted 

 for on the assumption that they are the natural produc- 

 tion of certain defined mechanical forces. Prof. J. .A. 

 Miller examined the excellent series of corona photographs 

 now available at the Lick Observatory, and he publishes 

 the results of his discussion in No. 4, vol. xxxiii., of The 

 Astrophysical Journal. 



If the streamers are formed of particles ejected from 

 the sun under the influence of the solar rotation, of the 

 attraction and of the radiant pressure of the sun, certain 

 shapes should theoretically ensue, and the velocity and 

 direction at any point of the stream can be calculated. 

 Prof. Miller has done this, and finds that not only do 

 the observed streamers largely conform with his theoretical 

 results, but he is able to compute and draw theoretical 

 streamers, for the conditions obtaining at any one eclipse, 

 which agree with those actually observed. Various 

 modifications occur, but may be accounted for by reason- 

 able assumptions of modified conditions ; for example, the 

 particles at the end of a stream are probably finer than 

 those at the base, and therefore the sun's radiant pressure 

 would act more strongly on them, or it may be that the 

 particles of a stream are moving in a resisting medium 

 which is denser in the inner than in the outer corona, and 

 each of these causes would produce the differences observed 

 between the computed and the observed results. 



The General Perturbations of Eros. — A lengthv dis- 

 cussion of the general perturbations of the planet Eros is 

 published by Herr H. Samter in No. 4498 of the Astrono- 

 mische Nachrichfen. The author tabulates his results for 

 the combined perturbations by Jupiter, Saturn, and Venus, 

 which were easily determined by Hansen's method, and in 

 further tables gives the results of the earth's perturbations 

 and those of Mars. 



Determination ok the Apex. — Frcmi the study of 620 

 stars having large proper motions. Dr. A. Wilkens has 

 made a new study of the position of the apex. The stars are 

 given in the Wilkens catalogue of 620 stars between 29° 50' 

 and 35° 10' N., for 1875, and the Leyden .A.G. catalogue, 

 and include 267 having proper motions of o'— 5* ; 173, 

 5''-io'' ; 76, lo'-is* ; 35, i5*-2o'' ; and bq greater than 20' 

 per century. They also include 233 stars brighter than 

 8-5, but mostly fainter than 75, mag., 282 between 8-5 

 and 90 mag., and 105 fainter than the ninth magnitude. 

 The resulting value for the position of the apex is 

 .\ = 286°, D = -|-37°, which is in good agreement with most 

 modern estimations {Astronomische Nachrichten, No. 

 4499), 



The Spectra ok Comets. — Visual observations of the 

 spectra of comets 1908 III. (Morehouse), 1909c (Halley), 

 and 1910a, are recorded by Herr von Konkoly in No. 4490 

 of the Astronomische Nachrichten. Bands were measured 

 at 5610 fifi, 5440 u^, and 515 nn in the spectrum of 

 1908 III. on September 18, 1908, their respective intensi- 

 ties being 04, 0'(i, and i-o; the same bands were seen on 

 September 22, but the wave-length in each of the last 

 two was I fi/i less. The red end of the spectrum was 

 much brighter than the violet, and of the band at 470 fifx 

 there was no trace. 



Halley's comet on February 12 and May 26, 1910, gave 

 a faint spectrum in which the same bands, with slightly 

 varying wave-lengths, were seen. With a larger instru- 

 ment, two other bands at 586-0 mi and 472 a>u were seen, 

 and possibly a third at 482 mm- The bands were very 

 bright while the continuous spectrum was abnormally 

 faint. From nineteen separate observations, the wave- 

 lengths of the bands in Halley's comet were found to be 

 586-0, 561-5, 543-7, 5x4-7. and 472-0 MM- 



The spectrum of comet igioa gave bands at 5s6>o, 

 5370. 51^-0, and 481-0 MM- 



