470 
Fig. 260. 
vertical line, not only the time of swinging 
the leg has increased, but also the time in 
which both legs are resting on the earth; for 
the latter commences at the instant when the 
forward leg has reached the ground, and termi- 
nates when the head of the femur has arrived 
at the vertical line, passing through the point 
of support of the same foot. The time aug- 
ments in proportion to the distance which the 
swinging leg passes beyond the vertical posi- 
tion, or half oscillation. The time when both 
legs are resting is greatest in fig. 260, because 
it must be sufficiently great for the head of 
the femur, together with the whole trunk, to 
advance to a position directly over the foot, 
during which the head of the femur moves 
very slowly, and by the direction of the for- 
ward leg its action is to retard the horizontal 
advance of the centre of gravity. The time is 
less in fig. 259, because the head of the femur 
has to pass through a less space, and the sup- 
porting leg acts against the trunk ata less 
angle; but in fig. 258 the time of both legs 
resting at the same time, disappears altogether. 
The two legs complete the least portion possi- 
ble of the vibrating curve, and the duration of 
each step amounts only to the time of half an 
oscillation. In walking very slowly we may 
suffer the swinging leg to vibrate so long, that 
it partly returns to its former position before it 
reaches the ground. 
We have seen in quick walking that during 
the time both legs rest on the ground, the ad- 
vanced leg continually forms a smaller angle 
with the vertical than the hinder leg; but in 
very slow walking the forward leg may form a 
greater angle with the vertical than the hinder 
leg; the magnitude of this angle determines the 
MOTION. 
kind of gait the walker acquires. In order t 
accomplish this, the swinging leg is suff 
nearly to complete its curve of oscillation be- 
fore it is placed on the ground, and during this 
time the centre of Bravity moves so little, tha 
half the length of the step may not be at one 
described, and the entire duration of the step wil 
be about four times greater than in the quickest 
pace.* In this case the forward leg really 
makes a greater angle than the hinder as | 
reaches the ground, but during the time thal 
both legs are on the ground, the angle of th 
forward leg diminishes, whilst that of th 
hina augments, = there is an instan 
when both legs form equal angles. When the 
angle of the forward leg | bncatlad zero, or in othe’ 
words, when it is directed vertically, the hinde 
leg rises from the earth; for example, in fig 
261, where a c represents the right leg, be 
the left, in the beginnin 
of a step, or the instant the 
foot a is raised from the 
ground ; ¢ c” is the magni 
tude of the step, or tl 
space which the centre ¢ 
gravity passes through i 
the time of a step, e” bein 
the centre of that spac 
Now, if the foot a, wh 
was raised at the begi 
ning of the step, were placed again on tl 
ground at a’, at the instant when the centre: 
gravity reaches the middle point c”, then bo 
legs would form equal angles with the vertic 
or, the angle b c’ a=a c” a, in wh 
c” w is the vertical through c”; but if the an 
of the hinder leg to the vertical be less, wh 
the right leg is set down in a’, the cer 
gravity will not have arrived at the 1 
point c”, but at c’; however, whilst both legs 
on the ground, the centre of gaia D 
pelled from c’ to c”, after which angle be’, 
Increases and the angle a c” @ diminis 
(where c’ @ is the vertical through ¢’); w 
the centre of gravity is propelled onwards fr 
ce” to ce”, the angle a’ c’ « is less than 6 c” 
until the termination of the step. . 
In this slow method of walking a very m 
sured pace results, in which the body is carr 
very erect, and remains for a considerable ti 
in the rear of the forward leg after it first rea 
the earth; consequently the duration of 
step will be very considerable, nearly one 
cond and a half, the length of the step 
short, and the velocity of the centre of gra 
which is very little at the middle of thes 
varies considerably during each step, so 
there is an instant in which the body is n 
at rest. This is denominated by Weber 
grave or procession step.+ . 
A remarkable difference may be obsery 
the duration of the steps of two different 
sons, one of whom has long and the other 
legs. In quickest walking the duratio 
* That is, where T represents the entire dw 
of an oscillation of the legs the time ofa step 
quickest to that in the slowest walking will 
4T to 2T, or four times that of quickest walk 
t Vide Weber, loc. cit. sect. 199, p- 344, 
a. 
asin 
