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facluriiig einiioiiiiuMU. These salts furnish electrolytes when ihe 

 humidity is relatively hi,i;h, dissolving; the copper at certain poorly 

 insulated points in the winding until the wire is eventually severed. 

 In tracing the sources of this type of corrosion, microtechnique has 

 afforded the only satisfactory method of attack. 



Recently studies have been made to learn the effects of the dusts 

 found in the telephone central office on the functioning of machine 

 switching equipment. In these studies, microchemical methods have 

 figured largely in the identification of the individual dust particles as well 

 as in the quantitative determination of the major type of components. 



