August 6, 1908J 



NA TURE 



335 



limit imposed in previous years to the number of hours 

 of instruction which may be counted for the purposes of 

 grant has been relaxed, a fact which will encourage local 

 education authorities to plan prolonged and well-organised 

 courses of evening instruction and help to remove a re- 

 proach that much of the work in evening classes has been 

 scrappy, unrelated to local industries, and not part of a 

 coordinated scheme. Greater encouragement than formerly 

 is being given to vacation courses for teachers, and the 

 sensible advice contained in the prefatory memorandum as 

 to the necessity of securing due recreation for teachers 

 during the progress of the holiday work deserves the 

 careful study of the organisers of such courses. It is now 

 laid down by the Board that there shall in future be a 

 principal, or head teacher, in those institutions where in 

 the past unrelated classes in charge of separate teachers, 

 responsible only to the managers, have been held. The 

 new regulation will, if the right type of head teacher is 

 appointed, lead to a greatly improved state of things. 

 Students will be able to receive much needed advice in 

 planning suitable courses of study to assist them in their 

 industrial pursuits, and the work of succeeding sessions 

 will form part of a complete scheme. The changes as a 

 whole are coUBeived in a broad spirit, and should assist to 

 develop still further the excellent work which is being done 

 in technical and other schools. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, May 7. — "A Tantalum Wave-detector, and 

 its .Application in \Mreless Telegraphy and Telephony." 

 Bv L. H. Walter. Communicated by Prof. J. A. Ewing, 

 C.B.. F.R.S. 



It has hitherto not been possible to employ a metal in 

 conjunction with mercury as a wave-detector which is 

 spontaneously restored to the sensitive condition, without 

 some artifice which assisted decoherence ; much less has 

 it been possible to use a noble metal for this purpose. The 

 only metal that has been found usable is iron, and this 

 latter is, owing to its tendency to rust, manifestly not 

 adapted to stand prolonged use, besides being otherwise 

 not satisfactory. 



The author has found that the metal tantalum gives an 

 effect with mercury which greatly exceeds that obtainable 

 with iron, the sound being very loud and of a pure tone. 

 The tantalum, in the form of a fine wire point, dips into 

 a pool of mercury so that the point is only just immersed. 

 An external applied potential difference of about 02 to 0-4 

 volt gives the best results, the tantalum point being con- 

 nected to the negative tenninal. 



-As now generally constructed, the device comprises a 

 glass containing-vessel into which are sealed two platinum 

 wires. One of these wires dips right into the mercury, and 

 serves to make contact therewith, while the other has its 

 end hammered out into a form of clip which is made to 

 hold the tantalum point. 



The level of the mercury is adjusted while the usual tele- 

 phone receivers are connected to the detector, and this 

 adjustment, when once properly carried out, during the 

 filling process, renders all further adjustment unnecessary. 

 The whole arrangement is hermetically sealed in the glass 

 bulb, which may previously have been exhausted. 



The detector has been tried at various wireless telegraph 

 stations, and has shown that for not too weak signals the 

 sound is several times louder than the same signals with 

 the electrolytic detector, it being understood that the most 

 suitable telephones for each type of detector are employed. 

 At a distance of 450 miles from a ship station fitted with 

 a 2-kilowatt plant the signals obtained on the electrolytic 

 and the tantalum detectors were of about equal loudness, 

 although in this case the telephones were not at all suited 

 to the tantalum detector. 



The device just described is rather sensitive to shaking, 

 and so a second form of detector is described which, owing 

 to its construction, is quite indifferent to vibration and even 

 to shock. Experiments were afterwards made with numer- 

 ous other metals, but no other case of an imperfect contact 



NO. 202,3, ^'OL. 78] 



of this nature was observed ; the behaviour of tantalum is 

 apparently unique. 



Froin the physical standpoint the chief interest lies in 

 the fact that by a suitable choice of materials it has been 

 possible to revert to the primitive simplicity of a metal 

 point in contact with another metal, and yet all the attri- 

 butes of a modern detector be retained. 



Edindurgh. 



Royal Society, July 7. — Pro'. Crum Brown. F.R.S. , in the 

 chair. — The craniology of the aborigines of Tasmania : Sir 

 William Turner, K.C.B. This race had become extinct 

 in 1877, and of the eighty skulls which were known to be 

 deposited in various museums of this country and the 

 Continent, no less than ten were in Edinburgh. The main 

 features of these dolichocephalic skulls were described in 

 detail, the curious roof-shaped top and the thick orbital 

 ridges specially being noted. A cast of the face which 

 belonged to the University Anatomical Museum was shown. 

 The woolly or frizzled hair which differentiated the Tas- 

 manians from all neighbouring races had been described 

 by several travellers. The question of the affinities of 

 the race was very obscure. All attempts to find relation- 

 ship with the indigenous races of the Malay Peninsula 

 and islands, with the Polynesian races, or with the in- 

 habitants of Australia or New Zealand, could not bear 

 close inspection. When first discovered by European 

 travellers, there could not have been more than 70,000 

 Tasmanians in an island almost as large as Ireland. 

 Throughout their isolation there must have been in-breed- 

 ing for centuries, leading to an accentuation of any pecu- 

 liarities which might have arisen, and so giving to the 

 race its own peculiarities. — Inversion temperatures and the 

 form of the equation of state : Prof. W. Peddle. It was 

 shown that a number of equations of state, all fairly 

 satisfactory otherwise as representative of facts, lead to 

 the conclusion that the inversion temperature of air de- 

 creases as the initial pressure rises, which is contrary to 

 Olszewski's experiments. Also the discrepancy cannot be 

 explained as due to difference of initial and final kinetic 

 energies. Some other source of error has probably affected 

 the results. Observations of the critical temperature and 

 its variation with pressure might discriminate among 

 various equations of state. — Magnetic quality in the most 

 open cubic arrangement of molecular magnets : Prof. W. 

 Peddle. It was found that such an arrangement, unlike 

 the closest packed arrangement, cannot explain the 

 magnetisation of magnetite, but presents analogies to 

 the magnetic properties exhibited by pyrrhotine. — Energy 

 accelerations and partition of energy : C. W. Follett. 

 From this discussion it appears that equipartition is not 

 possible amongst the freedoms in some of the cases. — 

 Combustion analysis : Prof. J. Walker and T. 

 Blackadder. The paper described certain modifications 

 of Liebig's method, which enabled the experimenter to 

 use a smaller combustion tube and to carry through the 

 operations in much shorter time and with less expenditure 

 of gas. 



P.ARIS. 



Academy of Sciences, July 27. — M. Bouquet de la 

 Grye in the chair. — The necessity of making use of the 

 three dimensions in space for the successive directions of 

 the two moving right lines joining the sun and a planet 

 to the earth, for determining in a simple manner the 

 relative variations of magnitudes of these lines : J. 

 Boussinesq. — The total sugar of the blood : R. Lepine 

 and M. Boulud. It has been stated by MM. Hugounenq 

 and Morel that larger amounts of sugar are found after 

 hydrolysis with hydrofluoric acid than with sulphuric or 

 hydrochloric acids, and they regard this as being due to 

 the less destructive action of the hydrofluoric acid. The 

 authors of the present paper confirm this fully, and have 

 applied this reagent to the determination of the virtual 

 sugar in the blood. Details of the technique are given, 

 and it is shown that the amounts of sugar obtained by 

 hydrolysis of the blood clot with hydrofluoric acid are of 

 the same order as those obtained from the serum, the sum 

 of the two representing the total sugar of the blood.^ — 



