The next stage is that of counting by the fingers, which gives rise to a natural system of decimal notation, as shown by such words as ten, which invariably means two hands; twenty, which is twice ten, and so on. Many existing races, who are a little more advanced than the Australians, use their fingers for counting, and can count up to five or ten, and even the chimpanzee Sally could count to five. But when we come to a duodecimal system we may feel certain that a considerable advance has been made, and arithmetic has come into existence as a science; for the number 12 has no natural basis of support like 10, and can only have been adopted because it was exactly divisible into whole numbers by 2, 3, 4, 6. The mere fact therefore of the existence of a duodecimal system shows that the nation which adopts it must have progressed a long way from the primitive "one, two, a great many," and acquired ideas both as to the relation of numbers, and a multitude of other things, such as the division of the circle, of days, months, and years, of weights and measures, and other matters, in which ready division into whole parts without fractions had become desirable. And at the very first in Egypt, Chaldæa, and among the Turanian races generally, we find this duodecimal system firmly established. The circle has 360 degrees, the year 360 days, the day 24 single or 12 double hours, and so on. But from this point the journey is a long one to calculations which imply a knowledge of geometry and mathematics, and observations of celestial bodies which imply a long antecedent science of astronomy, and accurate records of the motions of the sun, moon, and planets, and of eclipses and other memorable events.