vi PREFACE 



The descriptions given in the book of the systems 

 in use to-day will, I hope, make quite clear to the 

 reader " how it is done." Though certain portions 

 of the matter are intended for those already con- 

 versant with the general principles of electricity, the 

 bulk of the book has been written as simply as 

 possible, and if the said portions are just passed over 

 by the non-technical reader, I think the rest will be 

 of interest to him. 



At the time of going to press, preparations are 

 being made for an endeavour to transmit photographs 

 by wireless telegraphy across the Wash, the Post- 

 master-General having courteously allowed me the 

 use of the experimental wireless stations at Hun- 

 stanton and Skegness. The last chapter, therefore, 

 dealing with wireless work, will make the reader 

 acquainted with the latest phase of photo-telegraphic 

 work. 



T. THORNE BAKER 



15, GROSVENOR GARDENS, 



CRICKLEWOOD, N.W., 



March, 1910. 



