6.^o 



NA TURE . 



[October 27, 1904 



what has been encountered, and one is driven to the 

 conclusion that some portion of the thermal result is 

 due to the internal heat of the earth arising from 

 volcanic agency. 



The energy and skill of those in control, amongst 

 whom are Colonel Locher, Herrs Brandau, Pressel, 

 Kager, Sulzer, and many others, are surmounting 

 these difficulties, and it is anticipated that without any 

 very great delay the junction of the headings will be 

 effected. 



Certainly no tunnelling operations in any part of the 

 world have been exposed to such vicissitudes and 

 difficulties, and when the arching of the tunnel is fully 

 completed little will be left to show how hardly earned 

 has been the victory over physical obstructions. 



It is expected that within three months of the pierce- 

 ment trains will be running, and the railway will prove 

 to be a most important link in the line of communi- 

 cation between Rome, Genoa, and Milan with 

 Lausanne, Berne, and mid-Europe. Francis Fox. 



WATER-DROPPERS AND RADIUM 

 COLLECTORS. 

 T T IS more than forty years since Lord Kelvin com- 

 menced a new era in measurements of atmospheric 

 electric potential by devising the water-dropper. 

 Though marking a great advance, and simple in its 

 construction, the water-dropper has not increased the 

 happiness of those responsible for the conduct of self- 

 recording meteorological instruments. It has weak- 

 nesses which it takes some time to discover, and which, 

 when undetected, mav lead to serious error. Some of 

 the earlier forms had their water reservoirs so con- 

 structed that the pressure under which the jet issued 

 varied considerably with the time since the reservoir 

 w.-is filled. Punctualitv in filling the reservoir had in 

 this (;ase the disadvantage of accentuating a sub- 

 sidiary diurnal variation not due to nature. The mis- 

 directed attention of spiders, variations of moisture, 

 and other meteorological conditions, produce changes 

 of insulation in the water tank; choking of the jet 

 occasionally happens through impurities in the water 

 and in severe winters there mav be complete stoppage 

 through freezing of the jet. As this major catastrophe 

 usua ly occurs at night, it generallv entails a consider- 

 able loss of trace. 



The idea of replacing the water jet by some radio- 

 active substance presented itself pretty soon after the 

 announcement of Becquerel's discoveries. The report 

 of the International .Meteorological Committee, which 

 met at Southport in iqoj, contains a note bv Prof 

 J^ulsen on his early use of a radio-active powder. 

 Ihis was spread on filter paper resting on a disc of 

 copper, a thin covering plate of aluminium serving 

 as a protection against rain. In this form the 

 apparatus was used in Iceland in 1899-1900. M. 

 La Cour modified this form bv mi.xing the powder with 

 caoutchouc into a paste, which was' spread on a disc 

 ot copper, while a thin copper grating was pressed 

 down on the top of the paste before it was quite dry. 

 This form was used with satisfactory results in Fin- 

 land in 1900-1. After wetting bv rain, however its 

 efficiency was temporarily lessened. The same report 

 also describes an instrument which M. Moureaux had 

 hadin use for some time at Pare St. Maur Observatory, 

 Pans. It employs as collector chloride of radium iri 

 a shallow copper vessel, over which is soldered a plate 

 of aluniinium o-i mm. thick to keep out rain. Chloride 

 possessing 5000 times the activity of uranium was not 

 sensitive enough, but chloride with 30,000 times the 

 activity of uranium gave good results. M. Moureaux 

 so arranged matters that he could at pleasure record 

 NO. 18-: 6. VOT,. 70] 



the electric potential, practically at a fixed point, either 

 by the radium collector or a water jet. In this way he- 

 obtained an electrogram, successive portions of which 

 were obtained in immediate sequence bv the two- 

 collectors. Unless the times of the change had been 

 indicated, one could not have told by inspection of the 

 curve — which is reproduced in the report — which 

 collector was being used. When M. Moureaux's note- 

 was w-ritten the radium had been in use for several 

 months with satisfactory results. A foot-note, how- 

 ever, of later date, mentions that some months later 

 the radium was found to have produced a number of 

 minute holes in the aluminium, and that it was in- 

 tended to dispense with the aluminium and protect the 

 radium against rain by coatings of varnish. It was 

 further hoped that this would admit of the use of 

 cheaper chloride of less radio-activity. 



The employment of radium is thus hardly out of the 

 experimental stage, and any one adopting it at present 

 would be well advised to check the action from time to- 

 time by recourse to a water jet. It would also be 

 desirable to make sure before final adoption that the 

 radium does not itself modify the potential whicli it is- 

 desired to record, more especially in calm weather. 

 Whatever the final outcome may be, it is at least satis- 

 factory that M. Moureaux's experiments showed agree- 

 ment between the water jet and the radium collector 

 w-hen both were upon their good behaviour. 



C. Chree. 



NOTES. 



Tun friends of Prof. G. Carey I-'oster, F.R.S., are taking 

 the occasion of his recent retirement from the principalship- 

 of University College, London, as an opportunity of show- 

 ing their appreciation of him by promoting a fund with the 

 object of having his portrait painted for presentation to 

 the council of the college, and a replica for presentation to 

 Mrs. Foster. The president of the movement is the Right 

 Hon. Lord Reay, G.C.S.I., and the vice-presidents are Sir 

 Norman Lockyer, K.C.B., Sir Oliver Lodge, and Sir Arthur 

 Rijcker. Further information with regard to the scheme 

 may be obtained from the secretaries of the fund. University 

 College, Gower Street, W.C. 



The death is announced at Hamburg, on September 27, 

 of Dr. H. Kortum, professor of mathematics at the technical 

 college at Bonn. 



The Naples .\cadeniy of Physical and Mathematical' 

 .Sciences offers prizes of 500 francs to the authors of the best 

 papers in Latin, French, or Italian on the two following 

 subjects : the processes of formation of urea in the animal 

 organism, and the evolution of the ovaric ovum in the 

 .Selacii. The essays are to be sent in anonymously, bearing 

 a motto, on or before June 30, 1905. The Padua Society 

 of Encouragement offers, to Italian subjects only, two 

 prizes of 5000 francs for an essay on the present state of 

 the problem of electric traction on railways, and for a new 

 method of diagnosing the disease of pellagra previous to its 

 development. This competition closes on June 30, 1906. 



.\ PETiTio.\ has been presented to His Majesty in Council 

 asking for the grant of a charter of incorporation to the 

 South African Philosophical Society under the name of 

 " The Royal Society of -South .\frica." 



Mr. Wilfred Mark Webb has accepted the honorary 

 secretaryship of the Selborne .Society. 



The death is announced of Dr. Tillaux, professor of 

 surgery in the University of Paris, president of the Academy 

 of Medicine, and Grand Otlicer of the Legion of Honour. 



