PORTLAND,    NATURAL,    AND    PUZZOLAN    CEMENTS.  495 
testing  or  utilization.  A  brief  sketch  of  the  processes  of  Portland 
cement  manufacture  is,  however,  presented,  in  order  to  make  the  sub- 
ject clear  to  the  great  number  of  people  who  are  interested,  in  one 
way  or  another,  in  the  condition  and  growth  of  this  important  in- 
dustry. The  latter  portion  of  the  report  contains  comparatively 
brief  discussions  of  the  raw  materials  and  the  methods  of  manufac- 
ture of  two  classes  of  cements  allied  to  Portland  cement,  i.  e.,  natural 
Cements  and  puzzolan  (slag)  cements. 
While  the  report  above  described  will,  it  is  hoped,  prove  a  satisfac- 
tory summary  of  present  information  regarding  the  cement  resources 
and  cement  industry  in  the  United  States,  its  publication  will  by  no 
means  end  Survey  investigations  of  those  subjects.  As  fast  as  pos- 
sible the  principal  districts  will  be  examined  and  mapped  in  greater 
detail  than  has  been  heretofore  possible,  and  the  results  will  be  pub- 
lished in  the  form  of  separate  papers  or  bulletins,  supplementary  to 
the  report  above  noted.  The  present  bulletin  contains  several  such 
supplementary  reports,  dealing,  respectively,  with  the  cement  re- 
sources of  western  Virginia,  of  Mississippi,  of  New  York,  and  of 
Kansas. 
