370 



NATURE 



[May 20, 1920 



Our Astronomical Column. 



A Bright Fireball. — A splendid meteor was seen 

 on May 9, cjh. lom. G.M.I'., from Bristol, Cardiff, 

 London, Weston-super-Mare, and other places. 

 Special interest attaches to the object, for it appears 

 to have descended to very near the earth's surface, 

 if, indeed, it did not actually fall to the ground. The 

 meteor traversed a path of about 60 miles in 5^ 

 seconds, and fell from a height of 54 to 12 miles. 

 Combustion occurred over Radnor Forest, and the 

 meteor apparently disappeared over a point 10 miles 

 east of Barmouth. If the object was enabled to 

 travel in a compact form about 15 miles further, it 

 must have alighted on the ground in the region some 

 ten miles south of Bangor, Carnarvonshire, but no 

 intimation has yet been received that a meteorite has 

 been found, or was seen to fall, there. 



Conjunction of Mercury with e Geminorum. — 

 Mr. A. Burnet, of Oxford University Observatory, 

 makes a special study of occultations of stars by 

 planets. he now points out a close approach of 

 Mercury to the third-magnitude star c Geminorum 

 on June 11. The position of the star is R.A. 

 6h. 39m. 173s., N. decl. 25° 12' 33-8". Mercury is 

 in the same R.A. at 9h. 7m. G.M.T., 14* south. The 

 semi-diameter and parallax are 2-9" and 77", so that 

 an occultation will not happen at any part of the 

 earth. The hourly motion of Mercury is +i9-4S., 

 S-558". Hence conjunction in declination occurs at 

 8h. 52m. Micrometer measures of the differences of 

 R.A. and declination of planet and star will be of value, 

 especially as Mercurj- is a difficult object to observe 

 on the meridian. The sun sets in London at 8h. 14m., 

 and Mercury at gh. 50m. The times throughout are 

 given in G.M.T., not summer time. It is rather un- 

 fortunate that the date coincides with that of the 

 Royal Astronomical Society's meeting, as that will 

 prevent some astronomers from observing it. 



Longitude by Wireless Telegraphy. — This sub- 

 ject was discussed at the geophysical meeting at the 

 Royal Astronomical Society on May 7. Prot. Samp- 

 son, Astronomer-Royal for Scotland, pointed out that 

 wireless telegraphy supplied the long-sought desidera- 

 tum of signals that could be received simultaneously 

 over the greater part of the earth's surface ; in the 

 past eclipses of the moon or Jupiter's satellites, lunar 

 distances and occultations had been employed, but 

 the new method gave far higher accuracy. He 

 formulated a scheme in which three observatories at 

 longitudes some 120° apart, or, if preferred, four 

 observatories 90° apart, should each receive the signals 

 of suitably placed wireless stations and note their 

 local' time in the usual manner by meridian observa- 

 tions. The method would determine both the longi- 

 tudes of the stations and the periodic errors in' the 

 assumed clock-star places, since different clock-stars 

 would be on the meridian of each observatory at the 

 time of each signal. No extreme accuracy is called 

 for in the time of sending out the signal, since the 

 method is wholly a differential one. Interchange of 

 observers is not contemplated; this has hitherto been 

 the practice in longitude determinations, but the new 

 method contemplates using the ordinary observations 

 with the standard instrument of each observaton,' for 

 a considerable period. There will thus be several 

 observers, and if the travelling-wire method is adopted 

 very little error will be introduced by personal equa- 

 tion. Plans are already far advanced for connecting 

 Greenwich with Sydney in this manner. 



A demonstration' was' given of the method of record- 

 ing the wireless signals on a chronograph by the use 

 of a Fleming valve. The ticks of a chronometer, 



NO. 2638, VOL. 105] 



transmitted by a microphone attached to the glass, 

 were simultaneously recorded. The chief difficulty 

 was stated to be not the weakness of the transmitted 

 wireless signal, but the frequent confusion produced 

 by atmospherics. 



Periodicity in Weather and Crops, 



TT is generally understood that the principal source 

 *■ of terrestrial weather changes is to be found in- 

 solar radiation. Inasmuch, therefore, as the yield of 

 crops depends very largely on the weather, it is quite 

 natural to assume that any periodicity in the solar 

 radiation is likely to be reflected in the world- 

 harvests and the price of food. Many investigations 

 have had for their object the testing of a direct cor- 

 relation between solar activity, as evidenced by sun- 

 spots, and such terrestrial phenomena as the Indian 

 monsoon in regard to drought and famine. The 

 mechanism of world-weather is exceedingly complex,, 

 but progress is steadily being made in elucidating the 

 cause of the numerous departures from obedience to 

 any simple general law. 



The next step, after comparing terrestrial pheno- 

 mena with the known sun-spot period, was to analyse 

 various sets of data in search of unknown periodicities, 

 and Prof. Turner, for example, goes so far as to^ 

 connect what he calls "chapters" of meteorological 

 history with the movement of the earth's pole that 

 produces latitude variation. There is, however, one 

 very great difficulty in fixing any period the physical 

 basis of which is unknown, and that is the incom- 

 mensurability of all the suggested periods with that 

 of the earth's revolution round the sun. It is obvious- 

 that a dry period occurring exactly at sun-spot maxi- 

 mum, for example, if such a phenomenon should be 

 persistent, and if, which is another difficulty, the 

 sun-spot maximum were an exact predictable moment, 

 would have a totally different influence on the har- 

 vest according to the time of year at which the 

 drought occurred. The effect would also be quite 

 different in different parts of the world, notably on 

 the two sides of the equator. 



On Wednesday, May 12, Sir William Beveridge, 

 Director of the London School of Economics and 

 Political Science, delivered a lecture on the subject of 

 a hitherto unrecognised periodicity in the weather and 

 the crops. From the Times report of the lecture we 

 gather that he rather discredits the "sun-spot" in- 

 fluence, at least in the form advanced by Prof. Jevons 

 nearly half a century ago, and produces ostensibly 

 consistent evidence in favour of a period of 15J years 

 during the past three centuries. The argument rests 

 upon historic records of poor harvests, of Indian 

 famines, of tropical droughts and equally disastrous 

 wet summers in higher latitudes, and also to a great 

 extent upon official statistics of food prices. 



There is no indication in the report that attention 

 was paid to such obvious matters as war and plague, 

 which would have an enormous effect on prices. The 

 meteorologists of the next century will not, we hope, 

 attribute the high prices under which we are now 

 suffering to a periodic meteorological influence. Sir 

 William Beveridge has succeeded in setting forth a 

 list of dates at approximately equal intervals, and 

 claims that every one corresponds to a period of high 

 prices. He admits that there were other times of 

 similar conditions not belonging to the series he 

 claims to have discovered, and he also allows an 

 occasional uncertainty of something less than five 

 years, but he warns us to expect most unseasonable 

 weather, bad harvests, and high prices, with possible 

 famines, in one or more of the years 1924, 1925, and 

 1926. 



