These are the most frequently used words in this book.
actually
ago
almost
along
american
another
astronomers
away
best
between
big
building
called
came
city
clouds
come
course
day
down
earth
enough
even
ever
fact
far
few
find
first
fossils
get
go
going
good
great
happen
history
human
hundred
ice
island
itself
kind
know
lake
large
left
light
little
long
look
lot
may
miles
million
moon
mountain
museum
new
nothing
now
old
once
ones
own
part
people
place
planet
point
pretty
really
right
river
science
scientists
sea
see
since
sky
sometimes
space
stars
state
still
sun
surface
system
take
telescope
things
though
thousand
time
two
want
water
work
world
years