if the fish called a sea-star is
smeared with the fox's blood and then nailed to the upper lintel of the
door, or to the door itself, with a copper nail, no noxious spell will
be able to obtain admittance, or, at all events, be productive of any
ill effects."

It is easily comprehensible that a work fortified with such practical
details as this should have gained wide popularity. Doubtless the
natural histories of our own day would find readier sale were they to
pander to various superstitions not altogether different from that here
suggested. The man, for example, who believes that to have a black cat
cross his path is a lucky omen would naturally find himself attracted
by a book which took account of this and similar important details
of natural history. Perhaps, therefore, it was its inclusion of
absurdities, quite as much as its legitimate value, that gave vogue to
the celebrated work of Pliny. But be that as it may, the most famous
scientist of Rome must be remembered as a popular writer rather than as
an experimental worker. In the history of the promulgation of scientific
knowledge his work is important; in the history of scientific principles
it may virtually be disregarded.

PTOLEMY, THE LAST GREAT ASTRONOMER OF ANTIQUITY

Almost the same thing may be said of Ptolemy, an even more celebrated
writer, who was born not very long after the death of Pliny. The exact
dates of Ptolemy's life are not known, but his recorded observations
extend to the year 151 A.D. He was a working astronomer, and he made
at least one original discovery of some significance--namely, the
observation of a hitherto unrecorded irregularity of the moon's motion,
which came to be spoken of as the moon's evection. This consists of
periodical aberrations from the moon's regular motion in its orbit,
which, as we now know, are due to the gravitation pull of the sun, but
which remained unexplained until the time of Newton. Ptolemy also
made original observations as to the motions of the planets. He is,
therefore, entitled to a respectable place as an observing astronomer;
but his chief fame rests on his writings.

His great works have to do with geography and astronomy. In the former
field he makes an advance upon Strabo, citing the latitude of no fewer
than five thousand places. In the field of astronomy, his great service
was to have made known to the world the labors of Hipparchus. Ptolemy
has been accused of taking the star-chart of his