Acknowledgment  is  also  made  of  indebtedness  to  the
teachers  who  have  kindly  read  the  manuscript  and  offered
valuable  suggestions.
The  author  will  be  pleased  to  receive  any  constructive
criticism  of  the  book.
WILLIAM  H.   DOOLEY.
NEW  YORK  CITY,
August  15,  1919.
SUGGESTIONS  TO  TEACHERS

The  arrangement  of  this  book  is  such  that  it  may  be  used
equally  well  by  science  teachers  in  the  regular  secondary  and
technical  schools  and  by  science  teachers  in  vocational
schools.  When  used  in  connection  with  a  year's  course  in
industrial  science  in  the  technical,  industrial,  or  manual
training  courses  of  regular  secondary  schools,  it  will  aid  in
correlating  the  principles  of  science  with  shop  observation  and
experience.
The  method  of  presenting  the  subject  of  industrial  science
in  a  vocational  school  should  be  different  from  the  method
used  in  the  regular  high  school,  since  there  is  a  wide  difference
both  in  the  aims  of  the  courses  and  in  the  types  of  pupils.  In
the  vocational  school  it  is  well  to  consider  first  the  practices
pf  the  trades  and  industries  as  based  on  practical  shop  ex-


viii  SUGGESTIONS  TO  TEACHERS

perience  and  laboratory  work,  and  from  them  to  draw  out  the
principles  of  science  involved.
To  illustrate:  In  considering  the  properties  of  matter  in  a
metal  like  copper,  present  first  the  uses  of  copper;  it  is  used,
for  instance,  in  the  manufacture  of  sheet  metal  and  wire.
To  be  used  as  sheet  metal,  it  must  be  capable  of  "  being
worked/'  that  is,  hammered  into  sheets — it  must  be  malleable.
