490 



NATURE 



[December 31, 1914 



A NEW Diesel marine engine, built by Messrs. Dox- 

 ford and Sons, of Sunderland, is described in the 

 Engineer for December 25. In this engine the com- 

 plicated cylinder cover casting with its valve arrange- 

 ments is got rid of by having two pistons in the 

 cylinder working in opposite directions. The upper 

 piston is attached by a piston rod to a compensating 

 arm. which is connected by two rods, one on each side 

 of the cylinder, to two cranks placed at 180° to a 

 central crank; the lower piston is connected in the 

 usual manner to the central crank. The various 

 operations in the cycle take place between the two 

 pistons. The exhaust escapes through ports in the top 

 end of the cylinder; these are uncovered by the upper 

 piston when near the top of its travel. Scavenging 

 air is admitted through corresponding ports at the 

 bottom end of the cylinder ; these are uncovered by 

 the lower piston, and ensure a capital flow of scaveng- 

 ing air throughout the whole cylinder. The admission 

 valves are placed at the middle zone of the cylinder. 

 Cooling water is supplied to the lower piston through 

 a rocker arm, and to the upper piston through a tele- 

 scopic tube ; the latter arrangement is open to some 

 criticism on account of the diflficulty of preventing 

 leakage. 



The issue of " Hazell's Annual for 1915 " is now 

 ready. This is the thirtieth year in which this useful 

 " record of the movements of the time " has been 

 published. Some idea of the number of topics dealt 

 with may be formed from the fact that the index to 

 the volume contains close upon 20,000 entries. As is 

 natural, great prominence is given to facts in con- 

 nection with the war, but this engrossing subject is 

 not allowed to overwhelm the other matters of import- 

 ance dealt with in previous issues. A section entitled 

 "The March of Science," runs to about thirty-four 

 pages, and includes a summary of the proceedings at the 

 British Association meeting in Australia, and a 

 resume of progress in scientific research during 19 14. 

 We are glad of the opportunity to extend the praise 

 offered in these columns to the trustworthiness and 

 completeness of previous editions of the annual to 

 the present issue, the price of which is 3s. 6d. 



Mr. C. Baker, 244 High Holborn, London, has 

 issued his January list of second-hand scientific instru- 

 ments which he has on sale or for hire. Particulars 

 are given of more than 1500 pieces of apparatus, pro- 

 minent among which are numerous microscopes and 

 telescopes and their accessories. Every instrument 

 is guaranteed to be in adjustment, and arrangements 

 can be made for workers in the country to have pieces 

 of apparatus on approval. 



OUR ASTRONOMICAL COLUMN. 



A Remarkable Meteor. — On Tuesday, December 

 15, at 6h. 25m. p.m., an extremely slow-moving 

 meteor was seen by Mr. W. F. Denning at Bristol, 

 and by Mrs. Wilson at Bexley Heath. It had rather a 

 long flight, and was much brighter than a first 

 magnitude star. The meteor was curious as belong- 

 ing to a radiant point in Aquarius at about 336°-i2°, 

 and at the same position as the July Aquarids. No 

 meteors have hitherto been recorded, so far as is 



NO. 2357, VOL. 94] 



known, from this radiant so late in the year. The 

 object of December 15 last had a height of from 

 sixty-seven to forty miles, its luminous course ex- 

 tended more than seventy miles, and its velocity was 

 fourteen miles per second. The meteor must have 

 been observed by many persons, the night being very 

 clear and the object a very conspicuous one with an 

 extensive trajectory. At the middle of December a 

 well-defined shower of slow meteors from between 

 a and P Persei at 48^ + 44° was prominently active. 

 This same radiant has been observed at many other 

 times of the year, but never before on December 15 

 and 16. 



Parabolic Orbits of Meteor Swarms. — In the 

 Publications of the Leander McCormick Observatory 

 (vol. ii., part 4) a paper on 126 parabolic orbits of 

 meteor swarms is published by Mr. Charles P. Olivier, 

 these deductions being inade by him from more than 

 2800 observations of meteors, the combined work of 

 the American Meteor Society. Mr. Olivier directs 

 particular attention to the excellent work carried on 

 by this society in spite of its youth, and hopes for 

 more ideal methods of work in the future. It may be 

 remembered that the author previously (191 1) published 

 a paper entitled " 175 Parabolic Orbits and other Re- 

 sults Deduced from over 6200 Meteors," which ap- 

 peared in the Transactions of the American Philo- 

 sophical Society, N.S. (vol. xxii., part i), and the pre- 

 sent contribution may be considered practically a con- 

 tinuation of the above, the first radiant here num- 

 bered, namely, 177, following serially the radiants 

 given in the 1911 publication. 



One of the chief problems of meteoric astronomy is 

 that of stationary radiants, and in many quarters it is 

 considered that many of them exist, while other 

 workers on theoretical grounds look upon them as 

 mathematically impossible except in a few cases. Mr. 

 Olivier attacks the problem by inquiring into the 

 method of the reduction of the radiant points, and 

 concludes that the usual process of combining observa- 

 tions of many successive dates, and radiants which lie 

 sometimes as much as 10° from one another, etc., 

 tend to influence greatly the result. His results, re- 

 duced separately for each date, "show almost no 

 evidence of stationary radiation, and so far as they go 

 may be considered to disprove its existence." Numerous 

 interesting tables accompany this paper, among which 

 may be mentioned that containing the 126 parabolic 

 orbits ; elements based on eight radiants suggesting 

 these meteors were originally intimately connected 

 with Halley's comet ; ten orbits belonging to the 

 main Perseid stream, confirming their connection with 

 comet 1862 III., or Tuttle's comet, and other tables 

 giving the magnitudes of the meteors seen, per- 

 centages of meteors of a given magnitude to the totals 

 seen, and their colour and duration. 



The Spectrum of 10 Lacert^.— The star 10 Lacertae 

 (R.A. 22h. 35m., declination +38° 32', magnitude 50) 

 displays a spectrum which is conspicuous for the 

 sharpness of the important line at wave-length 4686 

 and of the other lines of hydrogen and helium. This 

 star is therefore not only suitable for a good deter- 

 mination of its radial velocity, but affords an oppor- 

 tunity of obtaining an accurate measure of the 

 stellar wave-length of the line at 4686 and other 

 lines. Both these objects have been investigated by 

 Messrs. E. B. Frost and Francis Lowater, and the 

 results are described in the Astrophysical Journal for 

 October (vol. xl., No. 3, 1914, p. 268). The line 4686 

 is now generally regarded as a line in the principal 

 series of helium, and the laboratory work of Prof. 

 Fowler has consigned to it the wave-length 4685-90. 

 The line is recorded in the spectrum of the chromo- 



