THE FOURTH OBSERVATION.

THe manner of signifying any motion or at∣tempt by fire,* was of great use in the night sea∣son, where the fortification was of so large an extension: for fire in the night doth appear far greater then indeed it is; forasmuch as that part of the aire which is next unto the fire, as it is illu∣minated with the light thereof, in a reasonable distance cannot be discerned from the fire it self, and so it seemeth much greater then it is in sub∣stance. And contrariwise in the day time it sheweth lesse then it is; for the clear brightnesse of the air doth much obscure that light which pro∣ceedeth from a more grosse and materiall body: and therefore their custome was to use fire in the night, and smoak in the day, suting the trans∣parent middle with a contrary quality, that so it might more manifestly appear to the behol∣der.