moil understanding, so that the work will appeal not only to the 

 technically trained expert, but also to the beginner and the self. 

 t;m Mil practical man who wishes to keep abreast of modern 

 progress. The language is simple and clear; heavy technical terms 

 and the formula? of the higher mathematics have been avoided, 

 vet without sacrificing any of the requirements of practical 

 instruction; the arrangement of matter is such as to carry the 

 reader along by easy steps to complete mastery of each subject; 

 frequent examples for practice are given, to enable the reader to 

 test his knowledge and make it a permanent possession; and the 

 illustrations are selected with the greatest care to supplement and 

 make clear the references in the text. 



C. The method adopted in the preparation of these volumes is that 

 which the American School of Correspondence has developed and 

 employed so successfully for many years. It is not an experiment, 

 but has stood the severest of all tests- that of practical use w r hich 

 has demonstrated it to be the best method yet devised for the 

 education of the busy working man. 



C, t'or purposes of ready reference and timely information when 

 needed, it is believed that this series of handbooks will be found to 

 meet every requirement. 



