612
HISTORY OF ENGINEERING.
Book I.
i) I* l
PIPES TO CISTERN JN ROOF.
are supplied by a pipe fixed under the troughs ; the water is allowed to flow’ successivelyinto the cisterns* and is shut off as abov<\
Ventilating. — An artificial system of ventilation has been adopted, with a view toproduce at all times and seasons an abundant supply of fresh and wholesome air ; thishas been attended with some difficulty in a prison where each prisoner has a separatecell, and the window of that cell necessarily obliged, for the sake of security, to be closed.Health is of the first importance, and considerable attention has been paid to the subject;but there yet seems to be something wanting, on entering one of these cells, to make it ap-parent that a pure and agTeeable atmosphere is breathed. The objects aimed at have beenthe withdrawal of a stated quantity of foul air from each cell; the supply of an equalquantity of fresh air, without subjecting the prisoner to a draught; the means of warming it,when necessary, without injuring its qualities, or affecting its hygrometrical condition, andthe avoidance of additional facilities for the transmission of sound by the air channels orflues.
The apparatus for warming the air is placed in the centre of the basement story of eachwing : it consists of a case or boiler, to which a number of pipes for the circulation of hotwater are attached. In connection with it there is a large flue open to the external air,which is introduced through this opening, and, after passing over the surface of the boiler,turns, right and left, along a main flue, which runs horizontally under the floor of the cor-ridor, and from thence passes upwards, through small flues in the wall, which terminate