ABSTRACTS OF TECHNICAL ARTICLES 533 



nature of simultaneity, and the adoption of a definition of simultaneity which 

 violates the intuitive and common-sense meaning of that term. It is the 

 purpose of this paper to show that these transformations can be derived by 

 imposing the laws of conservation of energy and of -momentum on radiation 

 processes as developed by Maxwell's methods. 



The Efect of High Humidity and Fungi on the Insulation Resistance of 

 Plastics} John Leutritz, Jr. and David B. Herrmann. The decrease 

 in insulation resistance of methyl methacrylate, glass bonded mica, glass 

 mat laminate phenolic, phenol fabric, phenol fiber, and wood flour filled 

 phenol plastic is determined during prolonged exposure of the plastics to 

 fungi and 97 per cent relative humidity at 25 C. The same plastics with 

 fungi present also are exposed to 87, 76, and 52 per cent relative humidity to 

 study their recovery, and then re-exposed to 97 per cent relative humidity. 

 Samples with cleaned surfaces and with varnished surfaces are dried and then 

 exposed to fungi and high humidity. The insulation resistance of a fungus 

 network on methyl methacrylate is determined at 87, 76, and 52 per cent 

 relative humidity. 



Fungus growth occurs on all the test specimens except those with cleaned 

 or varnished surfaces. The decrease in insulation resistance is retarded by 

 the varnish. The degradation is due entirely to moisture. The rate of 

 recovery is dependent on the composition and structure of the materials. 

 None of the plastics is permanently affected by exposure to fungi and high 

 humidity. Cleaning of surfaces and removal of moisture restore the insu- 

 lation resistance to its original high value in every case. Water adsorption 

 and absorption, not fungi, are the critical factors in the deterioration of the 

 insulation resistance of these plastics. 



The Elastic, Piezoelectric, and Dielectric Constants of Potassium Dihy- 

 drogen Phosphate and Ammaniuni Dihydrogen Phosphate.^ W. P. Mason. 

 Measurements have been made of all the elastic, piezoelectric, and dielectric 

 constants of KDP and ADP crystals through temperature ranges down to 

 the Curie temperatures. The piezoelectric properties agree well with Muell- 

 er's phenomenological theory of piezoelectricity provided the fundamental 

 piezoelectric constant is taken as the ratio of the piezoelectric stress to that 

 part of the polarization due to the hydrogen bonds. It is found that the 

 dielectric properties of KDP agree well with the theory presented by Slater 

 based on the interaction of the hydrogen bonds with the PO4 ions. ADP 

 undergoes a transition at — 125''C which results in fracturing the crystal. 

 This transition cannot be connected with the H2PO4 hydrogen bond .system 



^A.S.T.M. Bulletin, January 1946. 

 8 Phys. Rev., March 1 and 15, 1946. 



