3i8 



NATURE 



[January 5, 191 i 



■cattle, and then distributed on the land of each owner 

 in turn. 



At the meeting of the research department of the Royal 

 Geographical Society on December 15, 1910, papers were 

 read by Miss M. Pallis and Mr. R. Gurney on the saline 

 water of that portion of the Norfolk Broads which is 

 drained by the rivers Thurne and Bure. Evidence was 

 brought forward to show that such salinity was only 

 directly due to the tidal water of the sea in the case of 

 the Bure, but in the basin of the Thurne salinity increases 

 inland, and is greatest in Horsey Mere, which is fed by a 

 layer of salt water which percolates from the sea coast 

 and extends to some height above low tide-level. Similar 

 ■ conditions were cited from Holland, where much attention 

 has been given to the mapping of such salt-water table. 



An article relating to the decrease, in recent years, in 

 the frequency and intensity of London fog appeared in the 

 Times of December 27, 1910. The statistics given, based 

 ■on information published by the Meteorological Office, are 

 illustrated by two diagrams, in which the prevalence of 

 fog and bright sunshine in London are shown, in triennial 

 .means, by curves. These diagrams are supplemented by 

 the following table : — 



Days Hours of bright 

 with fog sunshine 

 1st nme Winters, 1883-4 to 1891-2 ... 29-9 ... 55-6 

 2nd „ ,, 1892-3 „ 1900-1 ... 207 ... 70-1 

 3rd ,, ,, 1901-2 ,, 1909-10 ... IO-6 ... 93-5 

 The curve relating to fog shows an increase in frequency 

 •during the first nine years, a decline subsequently, rapid 

 at first, afterwards gradual. The curve of bright sun- 

 shine, although irregular, exhibits a tendency for an 

 increase during the twenty-seven years ; since the winter 

 of 1901-2, only one season had fewer than the normal 

 .record. Reference is made to a discussion on the subject 

 which took place six years ago at a meeting of the Royal 

 Meteorological Society, when the respective speakers 

 attributed different causes to the improvement in the air 

 of London. The opinion favoured by the writer of the 

 article is that the improvement is due to the more 

 vigorous enforcement of the smoke-prevention clauses of 

 the Public Health Act, the use of gas fires for heating 

 and cooking, and improved methods of lighting. As 

 regards the quality of London fog, these are probably the 

 true reasons ; fog, however, usually occurs when an 

 approximation to uniformity of pressure gives rise to a 

 state of stagnation in the atmosphere, and is frequently, 

 though not necessarily, associated with anticyclonic con- 

 •ditions ; moreover, the geographical position of London 

 favours the occurrence of fog. 



The present position of Antarctic meteorology is the 

 subject of an interesting and instructive article, by Mr. 

 R. C. Mossman, in the Quarterly Journal of the Royal 

 Meteorological Society for October last. He points out 

 that our knowledge of Antarctic climate, as relating to a 

 continental surface, depends on sledge journeys, the fixed 

 observing stations being largely affected by oceanic in- 

 fluences. One of the most striking features shown by the 

 records at the stations is the low summer temperature to 

 the north of the Antarctic circle, due to pack-ice and to 

 the frequency of fog in low latitudes. The useful tables 

 accompanying the work show that the lowest of the 

 annual mean temperatures was —1-3°, observed by the 

 Discovery, being 8-4° lower than that at Cape Adare, some 

 400 miles to the north. The absolute minimum, observed 

 by the same ship, was —58-5°, but considerably lower 

 readings were recorded on sledge journeys. Precipitation 

 is most difficult to estimate, owing to drifting snow ; in 

 the Victoria Land region the Shackleton expedition found 



^•o. 2149, VOL. 85] 



an annual fall equal to about gj inches of rain. .Th 

 author estimates the annual amount for the land surf;.i 

 of Antarctica at about 12 inches. The winds are from ., 

 easterly direction, but at heights exceeding 15,000 feet il, 

 air moves polewards. The Shackleton expedition reco. 

 nised two high-level currents, the upper from a norther 

 and the middle from a southerly quarter. The author 

 observes, that the subject requires further study, and that 

 after the Pole is reached there will be little inducemf-rr 

 for enterprises of a record-breaking character, and th 

 some solid scheme of purely scientific research could i 

 set on foot with some prospect of success. 



The resume of the meeting of the Soci6t6 frangaise '. 

 Physique on December 2, 1910, contains a short accou: 

 of M. Perot's paper on the luminescence of the mercu; 

 arc in vacuo. The observations were made on arcs form 

 in a spherical vessel 10 cm. diameter, the current flowii 

 along a diameter. At very low pressures the dischar;. 

 fills the whole of the vessel, and has a white appearam 

 As air is allowed to enter, the discharge concentrates its. : 

 and becomes a rose-coloured column not unlike the positi\ 

 column in a vacuum tube. Mercury is transported froi 

 the anode to the kathode. Water vapour destroys ili 

 luminescence. An examination of the green line of tl 

 spectrum shows that while the principal component 

 reversed and displaced towards the red as the pressure 

 increased, the principal satellite is unaffected by pcessur 

 When observed in light emitted in the direction in whit 

 the current is flowing and in the reverse direction, r 

 spectively, it shows that the luminous centres are travellin 

 with the current with velocities of 30 to 350 metres p' 

 second, according to the pressure. M. Perot conclud' 

 that the light emission is due to the mercury atoms set : 

 vibration b\' the impact of electrons, that these aton 

 encounter inert atoms which they set in motion withoi: 

 rendering luminous, and at each encounter the phase, bi 

 not the energy, of the vibration is changed. 



A NOTE in the Builder for December 31, 19 10, giv 

 account of a contradiction to the generally accepted id' 

 that asphalt paving or lining is a barrier to vegetatio; 

 The courtyard at the Bank of Italy, in Rome, includes 

 small garden planted with shrubs, and particularly wii 

 Dracaena and Chamaerops. Beneath the court is a bas 

 ment covered by masonry arches, the extrados of which is 

 protected by a layer of asphalt seven-eighths of an inch 

 thick, with the' object of preventing the percolation of 

 moisture into the chamber where documents are stored. 

 Some little time ago it was noticed that damp patch' - 

 had appeared on the ceiling, and that the size of the 

 increased rapidlj-. On removing the earth from above the 

 masonr)- it was found that several roots of Chamaerops 

 had penetrated right through the asphalt, the holes beiiK 

 of about 0-25 inch in diameter, and almost as clean as ; 

 bored by a tool. Being unable to pierce the masonry, tli 

 roots had forced their way between it and the asphal 

 and, some of them having perished, left holes, throug: 

 which water passed freely. 



Commenting on the accident on the Midland Railwn 

 at Hawes Junction, the Engineer for December 30, 191* 

 considers that the question of safeguards against fire i 

 trains after collision is not very easily settled. T!i 

 substitution of electric light for gas is a recommendatin 

 which does not meet the whole case. Live coals ejecte 

 from the fire-box by the collision have been responsib! 

 for starting fires ; it is on record that an electrical! 

 lighted coach was so destroyed in the Grantham accident 

 again, the two coaches which first caught fire at Cud- 

 worth were so illuminated. The small inverted incandes- 



