436  Some  Remarks  on  Grape  Culture.  {Amsiptr;i887?rm' 
fail  to  attain  in  more  southern  but  less  favorably  situated  localities. 
The  influence  of  the  lake  is  also  well  illustrated  in  the  freedom  from 
mildew  on  the  vines  which  are  planted  quite  close  to  the  water. 
Higher  up  the  valley  beyond  the  lake,  while  the  vines  are  equally  as 
healthy  on  the  hills  there  as  they  are  on  those  in  the  near  neighbor- 
hood of  the  lake,  the  plants  suffer  from  mildew  on  the  lower  grounds, 
showing  that  the  radiation  of  heat  from  the  water  during  night  has 
the  effect  of  preventing  dews  even  on  low  grounds  near  the  lake. 
Here  we  have  two  factors,  both  of  which  are  favorable  to  a  healthy 
condition  of  vines,  or  rather  they  prevent  mildew,  which  is  the  prime 
result,  if  not  the  cause  of  unhealthiness,  so  far  as  atmospheric  influ- 
ences are  concerned.  The  first  of  these  is  owing  to  the  elevation 
above  the  valley  ;  during  the  day  heat  accumulates  in  the  valley,  and 
forms  a  stratum  of  warm  air,  which  is  lifted  up  as  the  colder  air 
rushes  down  the  slope  after  sundown,  and  wherever  this  warm  air 
strikes  the  hillsides  dews  are  not  found. 
The  second  important  factor  is  the  influence  of  the  water  in  effect- 
ing a  healthy  condition  of  local  climate.  The  ameliorating  influence 
of  an  extensive  body  of  water  is  well  understood,  and  a  noted  illustra- 
tion of  its  value  is  found  on  the  shores  and  on  the  islands  of  Lake 
Erie,  which  have  long  been  popular  for  the  extent  and  excellence  of 
the  vineyards  and  the  superior  qualities  of  the  fruit  which  they  pro- 
duce. This  success  is  fairly  attributable  to  the  modifying  effect  of 
the  body  of  water  upon  the  atmosphere,  which  secures  a  comparative 
immunity  from  heavy  night  dews  during  the  season  when  vegetation 
is  most  active.  1  he  heat  which  the  water  accumulates  during  sum- 
mer has  the  further  effect  of  warding  off  the  frosts  of  autumn  and 
early  winter,  thus  virtually  lengthening  the  season  to  an  equality  with 
the  climates  of  latitudes  several  degrees  southward,  so  that  grapes 
which  ripen  perfectly  in  the  vicinity  of  the  lake  fail  to  mature  in  lo- 
calities immediately  beyond  its  influence. 
For  all  cultural  purposes  it  is  sufficiently  accurate  to  assume  that 
the  hardiness  of  a  grape  simply  depends  upon  its  immunity  from  mil- 
dew. On  the  other  hand,  when  a  variety  of  our  northern  native 
grapes  is  said  to  be  too  tender  for  our  winters,  it  simply  means  that 
it  is  so  subject  to  mildew  that  the  growths  fail  to  ripen,  as  all  of  our 
native  grapes  of  the  Northern  States,  and  indeed  foreign  grapes  also 
will  stand  the  winters,  provided  their  young  yearly  growths  become 
thoroughly  matured ;  the  summer  climate  rather  than  the  winter  cli- 
