E. B. Hunt on Physical and Metaphysical Infinity. 3 
optical pereeption of perspective distances involves an 
| Pivaal process of reference of all dimensions seen, first to those 
| distances near at hand which are readily compre ehended, and in 
turn the reference of these to the actual lineal distance between 
the optical centres of the two eyes. This interocular pi or 
stereoscopic base line, bears the same relation to exteri 
distances that the base line in a geodetic triangulation does to the 
entire network of the angles. “Thus when we guage the per- 
spective of a landscape, there isa direct visual perception or 
“sensational measurement of external distances. Still we are so 
line that we do not make it an object of conscious ae 
tion, in our references of actin distances to this base as | 
unit of measure. Such a reference however really enters as 3 
vital part of every perspective perception, hence we are con- 
stantly applying unawares a standar measure, essen tially con- 
stant for each individual during his whole life, to all external 
| objects of our earthly surrou oundings. * In like manner the length 
of nee habitual step enters largely as a basis in our estimation of 
| distances because we are constantly measuring distances seen, 
| by Ser + habitual mechanism of locomotion. Thus all our means 
| of knowing external distances are found at last to rest solely on 
| the pian imensions of the human body to which as a standard 
' the rred. 
wbing into account all the elements of our perception of lin- 
eal magnitudes, it will be found without doubt that the average 
lineal unit is very nearly that length which is most readily cog- 
nizable by a man of average person and capacities. High multi- 
ples and low submultiples of the casniord of length are diffi- 
cult of appreciation; thus a mile or a line are much less clearly 
appreleen: ed units than a foot. If a thousand miles ora thou- 
sandth of a line is submitted to our consciousness, our notion be- 
comes extremely inadequate, and if it be a million or a millionth 
we fail almost entirely to conceive the fact. When it is a question 
of billions or trillions of miles our apprehension is so totally at 
fault that we give over all attempts to comprehend the fact, and 
so the distance becomes infinite for us, as referred to the mile as 
a unit. Onur real idea then is when we speak of an infinite or 
infinitesimal distance, that when it is compared with our famil- 
iar standard of length, our perceptive powers utterly fail to ap- 
preciate the relation with any approach to accuracy. 
If in place of the unity and infinity of distance, we consider 
those of time, space or force, we shall ‘find a like genesis of prac- 
tical standard units for each, based on the actual dimensions or 
sensational capacities of the human organism. Along the grad- 
uated line of connection between those values which by their 
pei 3 pry elude our perception and those vast values 
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