230  On  the  Construction  of  Farm- Buildings. 
the  timber  used  with  it  in  building  more  liable  to  decay  than 
when  used  with  brick.  Many  kinds  of  stone  exfoliate,  or  crumble 
by  the  action  of  the  atmosphere  ; and  in  rubble  buildings  of  stone, 
the  only  kind  of  stone  walls  of  which  the  cost  is  generally  less 
than  that  of  brick,  unless  the  mortar  be  of  the  very  best  quality, 
the  walls  closely  fdled,  have  frequent  thorough  bonds,  angles  well 
coigned,  and  the  returns  of  better  workmanship  than  usually  be- 
stowed on  rural  buildings,  stone  walls  are  very  much  weaker  than 
those  of  brick  ; whilst  with  any  deficiency  in  quality,  or  decay  of 
cement,  however  well  the  workmanship  may  be  performed,  rubble 
walls  are  a harbour  for  rats  and  mice. 
The  subject  of  the  present  section  has  perhaps,  so  far,  been 
treated  of  at  greater  length  than  to  many  may  appear  needful ; 
but  the  difference  between  the  expense  of  brick  and  rubble  stone 
walls  which  may  appear  in  the  estimates  to  be  stated  hereinafter, 
may  mislead  in  favour  of  the  latter,  whilst  in  reality,  all  advan- 
tages considered,  the  former  ought  decidedly  to  be  preferred  in 
the  erection  of  farm  buildings. 
The  timber  best  adapted  for  building  purposes  is  red  fir  from 
Norway  or  Sweden. 
Pillars  and  upright  supports  are  best  of  cast  iron.  Blue 
slate  is,  of  all  materials,  the  very  best  covering  for  roofs.  Tiles, 
and  artificial  roofing  made  of  Roman  cement  in  imitation  of  stone, 
are  neither  of  them  to  be  recommended,  as,  being  absorbent, 
they  are  liable  to  disintegration  of  their  substance  by  the  action 
of  frost.  The  different  kinds  of  roofing  which  have  of  late  years 
been  much  puffed  in  advertisements  under  the  appellation  of 
asphelted  felt,  &c.,  have  also  nothing  in  their  properties  to  recom- 
mend them  for  permanent  agricultural  buildings;  they  require 
sarking  under  them,  and  at  best  they  make  but  an  unsightly,  and 
frequently  a very  indifferent  covering.  The  article  in  question 
may,  however,  serve  sometimes  for  erections  of  a temporary  na- 
ture; but  where  cheapness  may  be  an  object  for  the  covering  of 
sheds  and  small  building,  reference  is  made  to  a mode  of  covering 
described  in  Appendix  A,  hereunto  annexed.  The  different 
materials  best  adapted  for  the  erection  of  farm-buildings  having 
been  noticed,  the  dimensions,  construction,  specification,  and  esti- 
mate of  the  cost,  will  next  require  consideration.  But  before 
treating  of  the  different  buildings  comprised  in  the  plans  to  which 
reference  has  already  been  made,  it  may  be  remarked  that  hipped 
roofs  are  to  be  preferred  to  roofs  with  gables,  as  being  neater  in 
appearance,  snugger  from  the  action  of  the  wind,  and  equally 
economical ; and  that  the  proper  slope  of  roof  is  that  on  which  a 
heavy  body  will  just  slide  on  its  surface  ; which,  on  a slated  roof, 
is  when  the  pitch,  or  height  of  the  ridge  above  the  walls,  is  one- 
third  the  outside  breadth  of  the  building. 
