March 6, 1913J 



NATURE 



eminent man on some aspect of Napier's life and 

 work; that, in response to an invitation from the 

 directors of Merchiston Castle School, a garden-party 

 be held in the grounds of Merchiston Castle ; that 

 papers be read on methods of calculation and of 

 mathematical teaching; that exhibits be made of all 

 kinds of calculating machines, of logarithmic and 

 other mathematical books which are necessary for 

 calculation, and of objects of historic interest 

 associated with the name of Napier ; that eminent 

 mathematicians be invited from foreign countries 

 to take part in the celebration; that a memo- 

 rial volume be published containing the more 

 important of the addresses and communications; 

 that, to meet preliminary expenses, a donation list be 

 opened, to which societies and individuals may con- 

 tribute ; that those interested in the proposal be asked 

 to become founder members, the subscription being 

 £2 ; and that the ordinary subscription be kept as low- 

 as possible. 



The executive committee was given powers to add 

 to its number and to appoint subcommittees to take 

 charge of the special departments of work indicated 

 above, and of any other lines of development which 

 might occur to them. 



THE METHOD OF "SHOCK-EXCITATION " 

 IN WIRELESS TELEGRAPHY. 



IN Die Naturwissenschaften of January 24 there 

 appears an excellent short descriptive article on 

 the principles and the advantages of the "shock-excita- 

 tion " method of generating electrical oscillations, 

 written by Dr. G. Eichhorn. The method of shock- 

 excitation is used in wireless telegraphy on the large 

 scale by the Gesellschaft fur drahtlose Telegraphie 

 ("Telefunken " system), and was first properly in- 

 vestigated and explained by Max Wien. Its essence 

 consists in using a very short-lived oscillatory dis- 

 charge in a primary circuit, to excite oscillations in an 

 antenna arranged as a secondary circuit, the life of 

 the primary oscillation being, in the ideal arrange- 

 ment, just so long as to admit of the transference 

 from primary to secondary of the maximum fraction 

 of the initial energy — that is, the energy stored on the 

 condenser in the primary circuit just before the be- 

 ginning of its discharge. The points especially dis- 

 cussed are the conditions governing, and the means 

 of realising, this ideal arrangement. 



Dr. Eichhorn starts with the fact that in a pair of 

 coupled circuits the phenomenon known as "beating" 

 takes place, and that in the time of a beat the oscilla- 

 tory energy passes from the primary to the secondary 

 and back again. The time of a beat depends on the 

 closeness of the coupling, being shorter with closer 

 coupling. But in the quenched spark method of 

 exi iting oscillations the stoppage of the primary oscil- 

 lation is effected bv cooling- the spark — that is to say, 

 by de-ionisation of the spark-gap — and the critical 

 moment for the stoppage is the first occasion on 

 which the whole energy passes from the primary to 

 the secondary, namely the moment of the middle of 

 the first beat in the secondary circuit. Thus the 

 better the quenching the closer can the coupling be 

 made. The author shows that the primary must be 

 tuned to the secondary the more exactly, the less 

 effective the quenching is. Among the advantages 

 claimed for the method that of economy is placed 

 first, and a comparison of published researches shows 

 that this method of shock-excitation may have an 

 efficiency of 75 per cent, as against the 25 per cent, 

 of the ordinary spark or the 10 per cent, of the 

 Poulsen arc method. 



.4 SUPERANNUATION SCHEME FOR 

 ENGLISH UNIVERSITY TEACHERS. 



r rHE advisory committee on the distribution of 

 1 Exchequer grants to universities and university 

 colleges in England has issued its second report 

 (Cd. 6617). In the first report it was recommended 

 thai a certain proportion of the grant of 149,000/. 

 available for distribution among the English colleges 

 should be reserved pending consideration of a super- 

 annuation scheme, and should be regarded as applic- 

 able to the institution of such a scheme and to other 

 purposes. 



Several conferences have been held between a sub- 

 committee of the advisory committee and representa- 

 tives of the universities and colleges concerned, exist- 

 ing schemes have been examined, the possibility of 

 a federated scheme has been considered, and the 

 present report gives the governing principles which 

 the committee suggests should underlie each scheme. 



I. Scope. — (a) The new scheme should come into 

 force on October 1, 1913, when — 



(1) It should be compulsory on all new entrants in 

 receipt of a salary of not less than 300Z. a year. 



(2) All new entrants in receipt of less than 3001., but 

 not less than 200!. a year, should be entitled to join 

 the scheme. 



(3) Any new entrant in receipt of less than 200L, 

 but not less than 160/. a year, should, with the consent 

 of the governing body, be allowed to join the scheme. 



(4) Any member of the existing staff who satisfies 

 the salary conditions under (i)-(3) above should, with 

 the consent of the governing body, be allowed to join 

 the new scheme under such provisions as to his in- 

 terest (if any) in any existing scheme of superannua- 

 tion as may be approved by the governing body. 



(b) Provided always that no member of the staff 

 should have a claim' for inclusion in the scheme who 

 does not, in the opinion of the governing body, devote 

 his main time to his duties as a member of the teach- 

 ing or administrative staff. 



II. Contributions. — (a) The total contributions in all 

 cases should be 10 per cent, of the salary, except that 

 in the case of salaries above 1000?. a year no con- 

 tributions should be made in respect of the excess 

 above 1000?. 



(6) The normal contributions should be 5 per cent. 

 of salary bv the beneficiary and 5 per cent, by the 

 institution, " but if the governing body desire, it 

 should be able to increase its proportion of the to 

 10 per cent, and diminish correspondingly the propor- 

 tion pavable bv the beneficiary. 



(c) If a person is a member of the staff of two or 

 more institutions both within the federated system, 

 the combined salary should be taken into account and 

 the institutions should contribute pro rata. 



III. Benefits. — (a) The benefit should include an 

 annuity on reaching the age at which the benefit 

 matures, or, so far as the governing body thinks desir- 

 able in each case, an equivalent cash payment. The 

 beneficiary should, however, have the option of _ choos- 

 ing a form of provision which secures in addition a 

 benefit in the event of death. 



(b) The age at which the policies mature should be 

 fixed at sixtv. 



IV. Means of Securing the Benefit.— Every bene- 

 ficiary should have the option of securing his ben. IV 

 bv means of an insurance policy. The governing 

 body should have the power, however, if it thinks 

 desirable, in individual cases, and if the beneficiary 

 concurs, to accumulate the contributions by separate 

 investment in trustee securiti -s on behalf of the bene- 

 ficiary. These separate investment- may be in addition 



NO. 2262, VOL. 91] 



