Blackboards
The best material for blackboards is slate, which furnishes a surface that is not shiny and will not reflect the light. They can be washed and easily kept clean and thus lessen the nuisance of dust. Blackboards should never be placed between windows. When possible there should be no windows on the same wall because when pupils are looking at the board there should be no light shining in their eyes. The blackboards are best placed opposite the principal light.
Dustless chalk is best and the use of colored crayons made of arsenic or sulphide of mercury should be prohibited, since the dust from these crayons is poisonous.
The blackboards should be plainly visible to all the pupils and care should be taken that all writing or other work on the board is large enough for the pupils to see without eye strain. The distance of each pupil from the board should be governed by the strength of vision.