BUILDING  STONE. 
SLATE  INVESTIGATIONS  DURING  1904. 
By  T.  Nelson  Dale. 
In  the  spring  and  fall  of  1904  visits  were  made  by  the  writer  to 
all  the  principal  slate-producing  districts  of  the  eastern  States, 
except  those  of  Slatington,  Pa.,  and  of  eastern  New  York  and 
western  Vermont,  which  had  already  been  visited  during  recent 
years.0  The  object  was  to  collect  material  for  a  bulletin  on  the  slate 
deposits  of  the  United  States,  for  which  other  geologists  are  also 
preparing  papers,  and  which  is  expected  to  appear  in  1005.  In 
these  visits  special  attention  was  given  to  the  structural  features  of 
the  principal  quarries  and  to  tin4  collection  of  typical  specimens  for 
microscopic  analysis. 
In  Maine  all  the  working  quarries  near  Monson,  Brownville,  and 
Blanchard  were  visited.  The  striking  feature  at  all  these  places  is 
the  well-known  frequent  interbedding  of  the  slate  with  quartzite] 
accounting  for  the  high  cost  of  quarrying  and  the  high  price  of  the 
product,  which,  however,  is  justified  by  its  superior  quality.  The 
falling  in  of  the  side  walls  at  some  of  these  quarries,  owing  to  under! 
mining  along  steeply  inclined  bedding  planes,  involves  considerable 
losses  of  capital,  which  could  probably  be  avoided  by  occasionally 
employing  a  competent  mining  engineer  and  following  his  directions 
as  lo  where  to  leave  supporting  walls. 
The  Peach  Bottom  slate  belt  in  Harford  County,  Md.,  and  York 
County,  Pa.,  and  the  recently  reopened  quarries  near  Thurston,  in 
Frederick  County,  Md.,  were  also  visited.  Some  of  the  larger  quar- 
ries in  both  the  "  hard  vein  "  and  the  "  soft  vein  "  belts  of  Northamp- 
ton County,  Pa.,  were  examined. 
The  northern  Vermont  slate  belts  lie  on  the  east  side  of  the  Green 
Mountain  axis.  Black  slate  was  formerly  quarried  both  at  North- 
field  and  at  Montpelier,  in  Washington  County,  but  at  present  only 
one  quarry  is  in  operation — that   of  the  Vermont   Black  Slate  Com- 
"  See  page  193. 
486 
