Micro‐Photographical Methods: The Application of Modern Photo‐Microscopy in the Testing of Aeroplane Materials

THE old and time‐tried chemical methods of determination of the technological properties of materials have, during the last 15 or 20 years, been accompanied and perfected by physical methods, such as the X‐ray or Gamma‐ray methods (i.e. the so‐called macroscopic and microscopic methods of material testing). These new methods have been developed to such an extent that the modern manufacture of sensitive and complicated apparatuses, such as aeroplanes, seems practically impossible without these ingenious methods of “ physical analysis.” The microscopic methods of determination particularly have been developed to a high degree of perfection, due to an equally rapid development of microscopic apparatus and auxiliary materials which had become necessary when from being an exclusively scientific apparatus the microscope was transplanted into the industrial laboratories. Microscopic testing of materials in vertical and oblique illumination is an absolutely indispensable aid of all industrial laboratories of to‐day.