Air, Light and Efficiency Showing Influence of Sash Types and Building Design . Spiral and coum.(jnvoight used inplace oi idler for long lines ot sash. For vertical lines longerthan 100 ft. or sloping lineslonger than 50 ft., spirals andcounterweights should be usedin place of idlers at the endsof the lines. These apply aforce sufficient to balance theweight of the sash, leavingonly friction to be overcomeby the hand Compouiiil luNCTs of Pond < )pcratiiigDevice, showini^ position with sash closed.

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Keywords: ., bookcentury1900, bookdecade1910, booksubjectr, booksubjectwindows