Many persons object to windows being much open during the summer on account of the invasions of blacks. Many years ago I tried nailing up a guard of thin strong muslin, coloured green or red, which is certainly rather useful in defeating the largest soot-flakes, and does not exclude the air or light. It should be often changed otherwise the soot with which it becomes charged detaches itself by its own weight from the muslin and enters the room. Those London sufferers who use white curtains will find the few pence required for the muslin well spent on this harmless kind of - no pun, please - black guard.

It is said that the register in stoves should never be closed for the sake of ventilation; but I think that openings higher in the room where the air enters without passing over a field of soot are far better, and the air must be better and cleaner. The chance of a soot-fall with its penetrating odour, to say nothing of a sore down-draught of one's neighbours' smoke at any moment, renders an open register a very disagreeable means of ventilating a delicately-furnished room.

Hollow walls lend themselves better to purposes of ventilation than solid ones, and keep the room warmer in winter and cooler in summer, as the enclosed layer of air is comparatively a non-conductor of heat. They might be oftener used with advantage; especially for detached houses and those on a damp soil, as they effectually keep out damp; and they are said to keep out sound better than solid walls - which would be a blessing when the next-door neighbours like to play the piano, and think they can.

Punkahs in some mechanical form might also be used in this country for ventilation, particularly for crowded drawing-rooms, schoolrooms, and churches.