When a place cannot be kept free from mosquitoes the house may be protected, as in the experiments in Italy, by wire gauze at the doors and windows.
It is sufficient to look at wire gauze backed by the sky or by a flame, through a piece of blackened cardboard, pierced by a needle and held close to the eye.
Observed through this the structure of some wire gauze just disappeared at a distance from the eye equal to 17 in., the gauze containing 46 meshes to the inch.
The disk 32 operates the wire gauze screens for equalizing the brightness of the two stars under observation.
Another form of sensitive jet is very easily made by putting a piece of fine wire gauze 2 or 3 in.
