from a reliable wireless system. Apart from the value of such a system for transmitting news pictures, it would also be of great advantage to transmit to ships at sea photographs of criminals for identification purposes. In such a small volume as this it would be impossible to deal with the working of wireless apparatus and the many systems that have been devised for the transmission of photographs over metallic circuits. The Author has taken it for granted that other works have been studied in connection with these subjects, and will therefore only describe such apparatus as is likely to be of use in wireless transmission. At present the transmission of photographs by wireless methods is in a purely experimental stage, and this book will have served its purpose if it helps to put future experimenters on the right track and prevent them from making expensive and fruitless experiments, by showing them the right direction in which investigations are being carried out. As there is no claim to originality in respect of a good many pieces of apparatus, etc., described, I have not thought it necessary to state the various sources from which the information has been obtained.
M. J. M.
Ashford, 1916.
CONTENTS
| PAGE | |
| Preface to Second Edition | [v] |
| Preface | [vii] |
| CHAPTER I | |
| Introductory | [1] |
| Foreword—Early experiments—Advantages of Radio-Photography—Difficultiesin Cable working—Bernochi'sSystem—Knudsen's System. | |
| CHAPTER II | |
| Transmitting Apparatus | [13] |
| Wireless Apparatus—Preparing the Photographs—TransmittingMachines—Transmitting Apparatus—Effects ofArcing—Spark-Gaps—Contact Breakers—Complete Station—ProfessorKorn's Apparatus—Poulsen Company's PhotographicRecorder—Comparison of various systems—Practicalapplications. | |
| CHAPTER III | |
| Receiving Apparatus | [37] |
| Methods of Receiving—Author's Photographic Receiver—DecoheringApparatus—Description of Einthoven Galvanometer—Useof Galvanometer in Receiving—Belin's Applicationof Blondel's Oscillograph—Description of Charbonelle'sReceiver—Use of Telephone Relay—Description of TelephoneRelay—Telephotographic Receiver—Polarisation Receiver—Kathode-RayReceiver—Electrolytic Receiver—Atmosphericsin Long-Distance working. | |
| CHAPTER IV | |
| Synchronising and Driving | [63] |
| Driving Motors—Isochronising the Electrolytic System—ProfessorKorn's method—Description of Hughes Governor—Author'sSpeed Regulator—Problem of Synchronising—Methodsof Synchronising—Advances made in Radio-Photography. | |
| CHAPTER V | |
| The "Telephograph" | [74] |
| Author's System of Radio-Photography—Requirements—Advantages—Transmittingmachine—Description ofDifferential Relay—Wireless Receiving Apparatus—Photo-TelegraphicReceiving Apparatus—Circuit Breaker—FrictionBrake—Magnetic Clutch—Description of Isochroniser—Methodof working—Types of Nernst Lamp—Action of NernstLamp—Comparison of Actinic Value—Inertia of PhotographicFilms—Choosing Films—Speed of Films—Standard of Speed—ComparativeFilm Speeds—Effects of Minimum Exposure—Effectsof Maximum Exposure—Considerations in workingand choosing Films. | |
| APPENDIX A | |
| Selenium Cells | [109] |
| Nature of Selenium—Preparation of Selenium—Forms ofSelenium Cells—Action of Selenium Cells—Characteristicsof Selenium Cells—Effects of Inertia in Photo-Telegraphy—Methodsof counteracting Inertia—Sensitiveness of Seleniumto Light—Effect of Heat on Selenium. | |
| APPENDIX B | |
| Preparing the Metal Prints | [115] |
| Outline of Process—Line Screens—Choice of Camera—FixingLine Screen in Camera—Lenses and Stops—Takingthe Photograph—Copying Stands—Choice of PhotographicPlates—Sources of Illumination—Metal Prints—Coating theMetal Sheets—Sensitising Solution—Printing Operations—Developing—Intensifying—Precautionsto be observed inworking—Preparing Sketches on Metal—Apparatus for Reducingor Enlarging—Improvements to Copying Board—Lensesfor Copying—Formula for Copying. | |
| APPENDIX C | |
| Lenses | [126] |
| Action of Light—Law of Refraction—Lenses—Prisms—Actionof Lenses—Focal Length of Lenses—Formation ofImages—Apparent Magnitude of Objects—Real and VirtualImages—Formation of Virtual Images—Power of Magnification—Defectsof Lenses—Aberration. | |