Foreword 



N recent years, such marvelous advances have l>een 

 made in the engineering and scientific fields, and 

 so rapid has been the evolution of mechanical and 

 constructive processes and methods, that a distinct 

 need has been created for a series of practical 

 working gulden, of convenient size and low cost, embodying the 

 accumulated results of experience and the most approved modern 

 practice along a great variety of lines. To till this acknowledged 

 need, is the sj>ecial purpose of the series of handbooks to which 

 this volume belongs. 



C, I" the preparation of this series, it has been the aim of the pub- 

 lishers to lay special stress on the practical side of each subject, 

 as distinguished from mere theoretical or academic discussion. 

 Each volume is written by a well-known expert of acknowledged 

 authority in his special line, and is based on a most careful study 

 of practical needs and up-to-date methods as developed under the 

 conditions of actual practice in the field, the shop, the mill, the 

 power house, the drafting room, the engine room, etc. 



4L These volumes are especially adapted for purjwses of self- 

 instruction and home study. The utmost care has been use<i to 

 bring the treatment of each subject within the range of the com- 



