56 J\^ew Publications. 



pipe of sheet iron four inches in diameter, passes from the back 

 of each cell near its ceiling, into the centre wall, where it is sur- 

 rounded by masonry, and continued in the wall to its top in the 

 garret. The outer wall of the building, and that on the front end 

 of the cells, is carried three feet higher than the top of the upper 

 story of cells. On these two walls rest the timbers supporting the 

 ceiling of the hall. This elevation of the ceiling forms a pit-like 

 recess over the whole block of cells in the garret. In the ceiling 

 of the hall there is a row of ventilators eighteen inches square, 

 and twenty feet apart. A full supply of fresh air is received into 

 the garret, through openings made in the projection of the roof 

 over the building. The aggregate capacity of the ventilators in 

 the ceiling is about three times greater than that of those in the cells. 



" This experiment has proved entirely successful. The fresh 

 cold air of the garret falls into the pit above the cells, from whence 

 it descends into them through the ventilating pipes ; it there meets 

 and mixes with the warm air from the stoves in the hall, which 

 readily passes through the lattice work of the cell doors. The vi- 

 tiated and over-heated air passes off through the more elevated 

 apertures in the ceiling of the hall. The prison being steadily 

 heated to about 60° F., the mason work of the block of cells is 

 of course brought to the same temperature. The cool air descend- 

 ing through the ventilating pipes, which are surrounded by this 

 warmer masonry, will of course be raised in temperature in pro- 

 portion to the length of pipe through which it travels. Hence the 

 air which descends through a pipe about eighteen feet in length, 

 to reach the lower cells, will enter them with a temperature high- 

 er than that which enters the upper cells through a pipe but six- 

 teen inches in length. In short, the heated air from the stoves in 

 the hall enters the cells with a temperature raised in proportion to 

 their elevation, and its heat is there counteracted by its union with 

 a current of descending air, reduced in temperature, and increased 

 in quantity in a similar proportion. 



" The following sectional view of the arrangement of the cells, 

 with the pipes and apertures for ventilation, will assist in under- 

 standing the subject." 



