612 
ABSOLUTE FORCE OF MAN IN DRAWING. 
dynamometer to be on an average equivalent 
to 286 lbs. The best position of the body 
in this case is the erect, with the shoulders 
slightly inclined. The greatest average load 
which a man can support on his shoulders 
for some instants, is commonly reckoned 
330 lbs. ; and it is supposed that he can 
exert the same force in drav^ing vertically 
downwards ; but these results are not dyna- 
mometrically ascertained. 
The mean absolute force of man in draw- 
ing or ‘pulling horizontally was found by 
the dynamometer to be the same as that 
exerted m pressure with the hands, or 110 
lbs. The force of the horizontal pull in the 
strongest men was found to be only about 
20 lbs. more than the average ; while in the 
other modes of applying force, much greater 
differences occurred. The reason appeal's 
to be, that, in drawing, the force depends 
more upon the weight of the body than upon 
muscular force. 
5. Human Labour.'] The permanent 
force of men and animals cannot be accu- 
rately ascertained by the dynamometer ; it 
is only by a series of careful observations on 
daily labour, that we can arrive at the ave- 
rage useful effect of animal exertion. In 
order to compare the different estimates of 
the force of moving powers, Dr. T. Young 
assumed, as a dynamical unit, the mean 
effect of the labour of an active man working 
to the greatest possible advantage : this he 
considered to be a force capable of raising 
10 lbs. 10 feet in a second for 10 hours a 
day; or, 100 lbs., which is the weight of 10 
imperial gallons of water, 1 foot in a second, 
or 36,000 feet in a day; or, 3,600,000 lbs., 
or 36,000 imperial gallons, 1 foot in a day : 
this may be called a force of 1, continued 
for 3S,000 seconds. 
M. Schulze, of Berlin, made a series of 
valuable experiments, in order to determine 
the accuracy of Euler’s empirical formula, 
or rule expressing the relation between the 
force and the velocity of animal agents. 
From experiments on 20 men, of different 
sizes and constitutions, he found their mean 
absolute force, in lifting weights, to be 
about 250 lbs. ; and in a level pull, about 
100 lbs, when standing still, and holding a 
silken cord passing horizontally over a pulley 
fixed above a pit, into which weights were 
suspended at the other end of the cord. 
Their mean absolute velocity, that is, 
when unencumbered by any load, was next 
ascertained by experiments made on a level 
plain, where the men marched at a fail- 
pace, without running, for a period of 4 or 5 
hours. This velocity was found to be about 
5, 1-3 feet per second, or 320feet per minute, 
or 3, 7-11 miles per hour. 
6. Their mean relative or permanent 
force was next determined by comparing 
their force in turning an upright cylindrical 
machine, with that of the weight which 
made it revolve, suspended atone end of the 
cord above mentioned. This mean force 
was found to be equivalent to about 30 lbs., 
moving with a velocity of 2^ feet per second.* 
From numerous comparisons, Smeaton con- 
cluded that the mechanical power of a man 
is equivalent to 3750 lbs., moving at the ve- 
locity of one foot per minute : Mr. Tred- 
gold estimates from this conclusion, that the 
average mechanical power of a man is 31^ 
lbs., moving at the velocity of 2 feet per 
second, when the useful effect is the great- 
est possible ; or half a cubic foot of water 
raised 2 feet per second — a very convenient 
expression for hydrodynamical inquiries. 
This estimate is very nearly the same, there- 
fore, as that derived from M. Schulze’s ex- 
periments. Mr. Tredgold states, that if a 
man ascend a ladder vertleally, the velocity 
corresponding to the maximum of useful 
effect will be one foot per second, and the 
load double what he carries horizontally ; 
consequently, the average of useful effect is 
62f lbs., or 1 cubic foot of water raised 1 
foot per second. Dr. O. Gregory states, that 
according to the best observations, the mean 
force of a man at rest is 70 lbs., and the ut- 
most velocity with which he can walk is about 
6 feet per second, taken at a medium. He 
thence deduces 31, l-9th lbs. as the greatest 
useful effect which a man can exert when 
in motion ; the velocity being 2 feet per 
second, or rather less than 1§ miles per 
hour.f 
7. Dr. Gregory demonstrates the follow- 
ing mechanical theorems, and shows their 
applicability to the mean action of men and 
animals : — 1 . The absolute velocity of an 
animal is to its relative velocity, that is, 
when impeded fey a given resistance, as the 
square root of its absolute force is to the 
difference of the square roots of its absolute 
and relative forces. 2. The work done by 
an animal is greatest, when the velocity 
with which it moves is 1-3 of its absolute 
velocity ; or, when its relative force is 4-9 
of its absolute force. 3, The greatest use- 
ful effect is consequently 4-27 of the pro- 
duct of the absolute force and the absolute 
velocity. 
8. Sir John Leslie, J with his usual tact, 
has simplified Euler’s formula, as confirmed 
by the above experiments, and we may now 
express it in the words of the following 
• Philosophical Magazine vol. xxxix. No. 16S. 
t Gregory’s Mechanics, vol. i. p 349. 
^ Natural Philosophy, p. 281 . 
