a 
370 EF. B. Hunt on our Sense of the Vertical and Horizontal, 
. descent, quite suffices to make us wonder. ‘This diminution as I 
have repeatedly observed, when commencing a rapid run down 
hill subtmacts much from the force or shock of the footfalls. The 
skill of jugglers in balancing poles, and of. rope dancers in self- 
- balancing, are illustrations of the same gravity sensibility. When 
we consider the unconscious skill of the fingers of the pianist or 
compositor, and that in all habitual muscular acts, the tendency 
is to a mechanical or quasi involuntary action, it will not seem 
singular that our continuous life-long perceptions of gravitation in 
all our sensitive parts, should assume an obscure or latent form in 
our minds which would cause all its results or effects to seem 
ot I ascribe that sense of the vertical within the limits 
of t ody whenee we pass to an acquaintance with the same 
in as external world, entirely to this trained gravity sensibility. 
In the remarkable case of John Metcalf, who though blind, was 
long and successfully employed in locating new roads over Derby- 
shire peak, this gravity sensibility must have become particularly 
acute, as this only could his skill be fundamentally ascribed. 
e second causal stage in our perception of the horizontal 
visual. The testimony of the body to the direction of gravitation 
makes us aware of the angle between the vertical and the optic 
axes, by reason of the permanent organic relation between 
body and these axes. In our ordinary or erect position, the me 
of this angle or its value, when a perfect muscular canitianh 
prevails, is a right angle, and any departure from this mean is in- 
dicated by the sensations of the various muscles, which cause the 
elevation or depression of the optic axes. Thus our sensations 
alone suffice to indicate to us the vertical, and a visual horizon 
perpendicular to it; and these sensations, checked and verified by 
a life-long experience, acquire an accuracy of indication which 
would hardly be anticipated. 'T’o these sensational codrdinates, 
we spontaneously refer all external objects. There is very muc 
also in our ordinary perspectives, to suggest and indicate the true 
horizon. Water, as the broad sheet, the winding river and the 
tumbling brook, level bottom lands and broad prairies, continuous 
hill crests, isolated knolls, either directly present horizontal planes 
or give such logical indications of the em as the experienced eye 
ean readily interpret, so as to derive with much accuracy a true 
general horizon. Indeed, we seem never to look over an extend- 
ed view, without almost instantly defining with more or less pre- 
cision our supposed horizon. Our previous experience from trav- 
elling over ground, doubtless enters directly in our definite loca- 
tion of this mental horizon. Are we ina valley, we pass our 
horizon under most of the objects seen. Are we in a ml! le 
point of view, we pass it ina mean position. Are we on a hill 
top, we pass it tangent to the general sweep of the landscape. 
