PORTLAND,  NATURAL,  AND  PUZZOLAN  CEMENTS. 
As  noted  below,  the  production  in  the  United  States  of  these  three 
groups  of  cements  was  in  L903  valued  at  $31,931,341.  In  11)00  the 
value  amounted  to  only  $13,283,581.  In  both  its  total  value  and  its 
rate  of  growth,  therefore,  the  cement  products  of  the  country  form  a 
mineral  resource  which  demands  careful  attention  from  this  Survey. 
A  brief  sketch  of  the  work  already  accomplished  in  this  line,  and  of 
investigations  planned  for  future  held  seasons,  is,  therefore,  given 
below. 
During  11)03  and  the  early  part  of  11)01  most  of  the  cement-produc- 
ing districts  of  the  United  States  were  visited,  and  their  raw  materials 
and  processes  exajnined.  A  report  on  the  "  Cement  resources  and 
cement  industry  of  the  United  States''  is  now  in  press,  and  Avill  soon 
be  issued  as  Bulletin  No.  243. 
The  bulletin  referred  to  has  been  prepared  chiefly  in  order  to  give  in- 
formation on  cement  materials,  which  is  desired  by  two  classes  of  per- 
sons. First,  owners  of  lands  on  which  marl,  limestone,  or  clay  deposits 
are  found  often  inquire  whether  a  given  material  is  suitable  for  Port- 
land-cement manufacture.  In  response  to  such  questions  the  author  of 
the  report  has  attempted,  in  the  preliminary  chapters,  to  describe  the 
chemical  and  physical  properties,  which  a  Portland-cement  material 
must  have,  and  also  to  show  that  the  value  of  cement  material  depends 
almost  entirely  upon  location  with  respect  to  fuel  supply,  transporta- 
tion routes,  and  markets.  Second,  cement  manufacturers  and  those 
wishing  to  engage  in  the  cement  industry  often  inquire  concerning 
the  localities  in  some  given  State  or  group  of  States  where  cement 
jinaterials  will  probably  be  found,  and  desire  information,  in  advance 
of  actual  testing,  concerning  the  physical  and  chemical  character  of 
the  materials.  The  latter  portion  of  the  report,  dealing  with  the 
cement  resources  of  the  separate  States,  is  designed  to  furnish  infor- 
mation of  this  character. 
The  scope  of  the  report  is  fairly  well  defined  by  the  preceding 
statements.  It  is  intended  to  be  primarily  a  discussion  of  cement 
materials,  not  a  manual  of  cement  manufacture  nor  a  guide  to  cement 
494 
