December i, 192 iJ 



NATURE 



447 



It consists of a step-up transformer, condensers, spark- 

 gap, and transformer, and is arranged to work off 

 100-200, and 200-240 volts alternating currents, with 

 periodicities of 50-60. Bull. 40 S gives a list of 

 second-hand electro-medical apparatus, including X-ray 

 sets and accessories, all of which are guaranteed to 

 be in first-rate working order, and show considerable 

 reductions in price over similar new apparatus. 



We are indebted to a correspondent for the sug- 

 gestion that the name of Dr. Henry Charlton Bastian, 

 F.R.S., who died on November 17, 1915, should 

 be added to the "Calendar of Scientific Pioneers." 

 Bastian was not only a pioneer in neurology, but was 

 also well known as a supporter of the doctrine of 

 " heterogenesis, " and for his investigations regarding 

 I the origin of life. 



Our Astronomical Column. 



The December Meteors. — Mr. W. F. Denning 

 writes: — "This event is anticipated with unusual 

 interest this year on account of the brilliant and 

 abundant display observed in 1920. Earlv in the 

 morning of December 13 meteors were observed to 

 be falling at the rate of about five per minute, and 

 several observers who were not regular meteoric 

 students were attracted to watch the spectacle on 

 account of its special character. The probability, 

 therefore, that another rich return may take place 

 this year renders it necessary that the sky should be 

 attentively watched from about December 10 to 

 December 13. The meteors are moderately swift and 

 the radiant point is close to the star a Geminorum 

 at the time of maximum, but, like the Perseids of 

 August, the Geminids exhibit a radiant point which 

 moves eastward at the rate of about 1° per day. The 

 shower certainly begins early in December,' if not 

 late in November, but there appear to be few traces 

 of it left after the middle of December. 



"The Geminids have no cometarv connection so 

 far as we know, but it is highly probable that this 

 system had its derivation from a comet which either 

 belongs to a past, or the present, age, and probably 

 having a long period of revolution." 



The Origin of Comets. — The question whether the 

 comets oi long period belong to the solar system or 

 are visitors from outside has been debated in recent 

 years by many astronomers. Prof. G. Armellini con- 

 tributes another paper on the subject to the September 

 issue of Scientia. He points out the insufficiency for 

 this purpose of the method of special perturbations, 

 since this would have to be carried to an impracticable 

 length before it could decide the character of an orbit 

 at a great distance from the sun. Moreover, some 

 who have used the method have failed to take the 

 origin at the centre of gravity- of the solar system, 

 the result of this neglect being an apparent oscilla- 

 tion of the orbit from ellipse to hyperbola in a period 

 of twelve years owing to the displacement of the sun 

 by Jupiter. 



Prof. Armellini introduces a new argument in favour 

 of the origin of comets within the solar system, 

 asserting that the combined attraction of the stellar 

 system would tend to give closed orbits even to those 

 comets the paths of which are hyperbolic while near 

 the ^sun. The stellar attraction would be absolutely 

 negligible in the region of space over which ordinarv 

 computations have extended, but might become 

 sensible near the aphelia of the long-period comets. 

 The author appears to assert that the stellar attrac- 

 tion would in all cases reinforce that of the sun ; this, 

 however, seems not to be the case. The resultant 

 stellar action would evidently be verv nearly constant 

 both in magnitude and direction within the' region of 

 space in question ; hence it would strengthen the sun's 



NO. 2718, VOL. 108] 



action on one side, but weaken it on the other. Un- 

 fortunately, our knowledge of the stellar masses is 

 insufficient to form any estimate of the direction in 

 which the resultant acts. 



Prof. Armellini appears to make an illegitimate 

 assumption in treating the stellar action as directly 

 proportional to the distance from the centre of gravity 

 of the star-sphere. This law would hold inside a 

 homogeneous sphere, but not in a sphere where the 

 empty regions enormously exceed those occupied by 

 matter. 



Odservations of Mars at Flagstaff. — The obser- 

 vations of Mars carried on for so many years at Flag- 

 staff, Arizona, by the late Prof. Percival Lowell, are 

 still being continued. This is fortunate, for the 

 climate and the excellent 24-inch refractor by Alvan 

 Clark are both well suited to the work. Bulletin 

 No. 83 of the observatory describes the observations 

 made in 1920 by G. H. Hamilton, and reproduces nine 

 drawings made on dates between March 8 and May 26. 

 These dates converted into the Martian Calendar 

 (N. hemisphere), would correspond with July 8 and 

 August 18. 



The interesting feature of the opposition was the 

 unusual number of white markings near the east and 

 west limbs, which generally dispersed, or diminished 

 in size, on the central meridian. As they appeared 

 both over desert and dusky regions, and as the canals 

 could be faintly seen through them, it is concluded 

 that they were cloud or mist rather than ground 

 frost. Even the Syrtis Major, usually so prominent, 

 was sometimes almost lost in mist. From the fact 

 that similar drawings were made in 1903 it is sug- 

 gested that the phenomenon may occur, at the same 

 calendar date in each Martian year, but is clearly 

 visible from the earth only once in fifteen years. 

 Attention is also directed to the fact that these whitish 

 areas are not surrounded by dusky borders, as they 

 would be if the theory were true that explains the 

 canals as the boundaries of regions of different tone, 

 showing up more distinctly from the effect of con- 

 trast. The absence of the dusky border also supports 

 the objective reality of the dark border round the polar 

 cap. 



It was also noted that some of the dusky regions 

 looked unusually dark after they had been cloud- 

 covered, suggesting growth of vegetation after rain. 

 Altogether the observations support the view that 

 there is more "weather " on Mars than has recently 

 been thought probable. However, Mr. Hamilton 

 quotes some similar observations made by Sir Xorman 

 Lockyer in the last centur\'. from which Sir Norman 

 concluded that the seasonal changes of Mars are very 

 intense. 



