151 If the lower sash is raised just enough not to let air into the 
room above this strip, then a current of air will flow into the room between 
the upper and lower sash, and will shoot upwards so as not to
annoy the occupants of the room as when a sash is raised or lowered. 
This action of a ventilating board is old, where the lower sash rests 
on the board, and it is necessary to remove the board to fasten the 
sash or blinds. 
On the 27th I saw at the residence of Mr. Crandall all his windows fixed 
with the top of the upper sash made so as to allow four inches to run up 
into a groove, so that the upper sash could be lowered and the [illegible] on 
[illegible] the upper part of the sash might go six or more inches into this 
groove. This he got from an English writer on Health of homes, and is the 
plan when a new building is erected. 