This method is frequently adopted in combined schemes of heating and ventilating; the fresh air is warmed by being passed over their surfaces previously to being admitted through the gratings into the room.
This opisthodomus was completely fenced in with bronze gratings; and the excavators believe it to have been adapted for use as an adytum (shrine).
The houses, built of stone and whitewashed, are square, substantial, flat-topped buildings, presenting to the street bare walls, with a few slits protected by iron gratings in place of windows.
But, except perhaps in the case of very fine gratings, it is probable that the error thus caused is insignificant; for the incorrect estimation of the secondary waves will be limited to distances of a few wave-lengths only from the boundary of opaque and transparent parts.
It is true that in 1823 Fraunhofer, inspired by his observations upon gratings, had very nearly hit the mark.'