‘ 1823. ] 4 
interfere with the governor’s view of the 
prisoners, nor to lessen the security of 
the yards. ; ’ 
The tread-wheel is set to work in the 
following manner. The party of pri- 
soners ascend at one end by means of 
steps; and, when the requisite number 
are ranged upon the wheel, it com- 
mences its revolution. _ The effort, then, 
‘to each individual of the party, is 
simply that of ascending an endless 
flight of steps, the combined weight of 
the prisoners acting upon every succes- 
sive stepping-board, precisely as a 
stream of water upon the float-boards of 
awater-wheel. This operation is main- 
tained without intermission during the 
hours of labour, by the appointment of 
a certain portion of the class to relieve 
the party on the wheel. These changes 
‘are performed at regular intervals dceter- 
mined by signal: when the prisoner at 
one end of the wheel descends for rest, 
another at the same moment ascends at 
‘the opposite extremity of the wheel, as 
represented in the frontispiece.* By 
this method, the proper number of men 
on the wheel is continually kept up, and 
the work is equally apportioned to 
every man. The degree of labour to 
each prisoner in a given time is also de- 
termined with great precision, by regu- 
Jating the proportion of working and 
resting men one to the other; or, which 
amounts to the same thing, the relative 
- proportion of those required to work the 
wheel with the whole number of the 
class; thus, if ten out of fifteen men are 
appointed to be on the wheel, each man 
will haye forty minutes’ labour, and 
twenty minutes’ rest, in every hour. 
In order to guard against interruption 
to the regular employment of the prison- 
ers on the tread-wheels, which might 
happen from the supply of werk in the 
‘mill at any time falling short, a fly- 
wheel is attached to the principal shaft 
in the mill-honse, which is represented in 
the frontispiece on the roof of the build- 
ing. The fly-boards of this wheel are 
connected with a pair of regulating balls, 
which, as the velocity of the wheel in- 
creases, tend by their centrifugal action 
to expand the fly-boards; by these 
means, ihe requisite degree of resistance 
is presented to the motion of the tread- 
* At the Bridewell in Edinburgh, these 
changes ave announced by means of a bell 
attached to the machinery; the bell is ca- 
able of being set so as togive the’signal at 
intervals of any length that may be 
desired, 
Moyrury Maa, No, 385, 
‘ 
Prison Amelioration Society. 
57 
wheel machinery, and the labour of the 
prisoners suffers no interruption.* 
In the application of human exertion 
to this species of mechanical labour, 
there are two olijects to be considered 
as affecting the measurement of such 
exertion ; first, the rate or velocity with 
which the exertion is maintained; se- 
condty, its duration. The rate of exer- 
tion niaintained by a prisoner on the 
tread-wheel will be determined by the 
velocity of its revolutions, and by the 
height of the steps; thus, if a prisoner 
treads upon the steps of a whee! which 
are cight inches asunder, and if the 
velocity of its revolution be fifty steps 
per minute, lic will have to move or lift 
his own weight over 334 feet per 
minute, or maintain a rate of exertion 
equal to 2000 feet of ascent per hour. 
To complete the measure of individual 
labour, the duration of this rate of exer- 
lion is next to be considered. This 
will be affecled by the proportion of 
resting and Jabouring prisoners, in which 
a class or gang may be appointed tu 
work on a tread-wheel, and by the num- 
ber of hours which the regulations of the 
prison require for daily labour at differ- 
ent seasons of the year. Thus, if two- 
thirds of a class are appointed to be on 
the wheel, and one-third to be off as 
relays, and if the number of hours of 
general labour for the day be ten, as in 
the summer season, the duration of 
aciual labour to each man for that day 
will be 63 hours, with 34 hours of rest. 
Then, if the rate of exertion, 2000 fect 
per hour, be multiplied by the actual 
duration of it, viz. 63 hours, we shall 
have a result of 13,383 feet ascent as the 
measure of each man’s labour at the 
wheel for the whole day. ‘This measure 
in feet ascent may, therefore, be taken 
as the most simple and correct standard, 
for determining any quantity of actual 
exertion performed by a person working 
at the tread-mill. 
The quantity of mechanical power 
‘exerted in this instance would, without 
‘doubt, be measured more scientifically, 
by taking the product of the weight 
multiplied by the space over which that 
_—_—_——__ 
* At Cold-bath Fields prison, a regu- 
lating fly is attached to the tread-wheel 
machinery, by which the power derived 
from the action of abont 240 prisoners is 
expended jn the air. The resistance pre- 
‘sented by the action of a fly increases with 
its velocity; and, after a certain time, that 
resistance becomes so powerful as to pre- 
ventall farther acceleration, when the mo- 
tion of the machinery remaing uniform. 
: I weight 
