equal. On the contrary, every black or white division 
is to be understood as meaning ten times as great a 
dimension as the division immediately below it and a 
tenth of the dimension of the division immediately above 
it. By this device it is possible in a diagram only about 
ten inches long to place in their relative order, in terms 
of a unit of one centimere, all conceivable: magnitudes 
from the limit of astronomical space down to the ulti- 
mate particles or wave-lengths of matter. Each of the 
large black or white divisions of the scale is an order of 
magnitude. Starting from the centimeter unit at about 
the lower third of the scale, 27 positive orders of 
magnitude stretch to the top .of the scale, the 27th order 
representing the extreme limit of space; and 14 negative 
orders stretch to the bottom of the scale, the 14th 
negative order representing dimensions smaller than the 
ultimate particles of matter. 
189. In order to represent every digit within each 
order, nine small divisions are marked on each main 
division of the scale. Starting from the centimetre unit 
these small divisions, reading upwards, represent 1, 2, 
3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 
100, 200 cm., and so on. - The actual reading of a dozen 
of these small divisions about the llth negative order 
are shown at the bottom right-hand corner of the 
diagram. 
190. Looking at the dimensions shown in the dia- 
gram those of which the index (the right-hand figure or 
pair of figures) is 1 may be called dimensions of the 
first order of magnitude (on a centimetre basis as unity). 
The first order includes dimensions from 10 cm. to 99 
cm.; the second order from 100 to 999 cm., and so on. 
Chapter V—Scale in Nature 
As examples of objects falling in these orders of magni- 
tude we may take the following: Zero or unit order,. 
a fingernail. First order, a fowl. Second order, a man, 
Third order, a house. Fourth order, a garden. Fifth 
order, a farm. Sixth order, a sheep station. Seventh 
order, Tasmania. Eighth order, Australia. Ninth 
order, the earth. Tenth order, moon’s orbit. Eleventh 
order, the. sun. Twelfth order, largest stars. Thirteenth 
order, earth’s orbit. Fifteenth order, the solar system. 
Twenty-second order, our universe (the Milky Way or 
Galaxy), and other universes (the spiral nebulae). 
Twenty-sixth order, distance of furthest spiral nebulae 
visible in largest telescopes, from which light takes 100 
million years to reach us. Modern physicists consider 
that there is a limit to tke total world of space; their 
estimates of this limit vary between the twenty-seventh 
and twenty-eighth orders of magnitude. 
191. Passing downwards from the centimetre unit 
through the increasingly minute negative orders, the 
following examples may be taken: First negative order, 
a grain of wheat. Second negative order, a human 
ovum (egg-cell). Third negative order, blood cor- 
puscles. Fourth negative order, bacteria (“germs”). 
Fifth negative order, wave-lengths of visible light. 
Sixth negative order, wave-lengths of ultra-violet light. 
Eighth negative order, size of atoms. Ninth negative 
order, wave-lengths of X-rays. Eleventh negative order, 
wave-lengths of Gamma rays. Thirteenth negative order, 
electrons and atomic nuclei. 
(To be Continued.) 
65. 
