84 



KNOWLEDGE. 



March, 1913. 



consisting of particles of galena and tellurium in 

 contact, which permits the current to pass, in one 

 direction only, through a " string " galvanometer. 

 A shadow of the string is projected on;to a moving 

 strip of sensitive paper, which passes on into develop- 



The system has been tried successfully between 

 Lyngby, in Denmark, and Cullercoats, at the mouth 

 of the Tyne. a distance of six hundred miles. 

 Whether it will work as well between Ireland and 

 North America remains to be seen. 



Figure 77. Poulsen M 



ing and fixing baths, so that a permanent record of 

 the vibrations of the string is obtained, similar 

 to that of Lord Kelvin's siphon recorder, which 

 is shown in Figure 75, at the bottom of page 82. 



California (U.S.A.) 



The merits of the various rival systems are still 

 sub judice. The brief sketch of one of them which 

 we have given may be helpful to some who are 

 interested in following the evidence. 



RESEARCH DEFENCE SOCIETY. 



We have received the following appeal from the Officers of 

 the Research Defence Society and have much pleasure in 

 commending it to the notice of our readers. 



To the Editors of " Knowledge." 



Sirs, — It is said that the fifth year, in the life of any 

 Society, is the critical period of its fortunes. The Research 

 Defence Society was founded on January 27th, 1908. To all 

 who are interested — and who is not ? — in medical research, 

 we beg you to let us say that the Society has its hands full of 

 work, and only wants more money to do more work. Much 

 has already been done, by lectures and by distribution of 

 literature, to bring home to people the truth about experiments 

 on animals in this country, and the great value of them, not 

 only to mankind, but also to the animal world. The expenses 



of our Society are heavy ; but the good results of our work 

 are extended far and wide. We have lately opened a Bureau 

 and Exhibition at 171, Piccadilly (opposite Burlington House). 

 We are exhibiting pictures, portraits, charts, anaesthetics and 

 inhalers, germs in pure culture, tsetse flies and mosquitoes, 

 and so forth. This little exhibition, every day and all day 

 long, displays to " the man in the street " the facts of the case. 

 We are the only Society which is doing work of this kind ; 

 but, of course, it cannot be done without money. Our record 

 for the last four years gives us the right to hope for a great 

 increase of our Membership, and of our funds, in the coming 



year " DAVID GILL, President. 



F. M. SANDWITH, Hon. Treasurer. 

 STEPHEN PAGET, Hon. Secretary. 



21, Ladbroke Square, W. 



