Abstracts of Technical Articles by Bell System Authors 



Electron Microscopes and their L'scs} Joskph A. Bkckkr and Arthur 

 J. Ahearn. Three and a half centuries have passed since Zacharias Janssen, 

 a spectacles maker of Middleburg, Holland, put two lenses in a six-feet- 

 long tube and thereby made the iirst known compound microscope. In 

 the years since then, the microscope, now grown into a powerful and in- 

 tricate instrument, has played an important role in the discovery of much 

 of man's knowledge of the physical world. There is, however, much that 

 the microscope has been unable to reveal because of its limited range of 

 useful magnitication. Today a new type of magnifying instrument, the 

 electron microscope, is extending the range of useful magnification far be- 

 yond its old limits and promises to supplement the traditional microscope 

 in many tields of scientific research. In this article the authors describe 

 types of electron microscopes, tell how they function, and outline how 

 they are being used in physics, chemistry, metallurgy and the biological 

 sciences. A number of pictures are shown to illustrate these uses. 



Recent Developments in Protective Metallic Coatings? R. M. Burns. The 

 prevention of corrosion is accomplished by two general methods: (1) the 

 provision of a non-corrosive environment, and (2) the interposition of 

 a protective film to exclude the corrosive environment from the metal. As 

 an example of the first method one may cite the de-aeration of boiler feed 

 waters and air conditioning in which moisture is controlled and dust, sulphur 

 gases, etc. eliminated. 



Referring to the second method, corrosion protective films may be di- 

 vided into two main classes: the first consisting of those films formed natu- 

 rally through the production of corrosion products on the surface of the 

 metal to give a thin protective coating; and second, comprising films of 

 paints, varnish, ceramic products or metals which themselves develop pro- 

 tective films. One natural type of protective film is the chemical con- 

 version coating produced by various treatments, such as phosphate or 

 chromate dipping or anodic oxidation. 



Zinc is the most important of metallic coatings, 45% of the metal con- 

 sumed in the United States being used in this manner. Hot galvanized 

 coatings on steel have been improved by suitable pre-treatment of the 



1 The Scientific Montlily, October 1941. 



^ The Monthly Review of the American Electro platers^ Society, September 1941. 



439 



