The Swaheli Numeral System
At the time when I was new in Africa, a shy young Swedish dairy-man was to teach me the numbers in Swaheli. As the Swaheli word for nine, to Swedish ears, has a dubious ring, he did not like to tell it to me, and when he had counted: “seven, eight,” he stopped, looked away, and said: “They have not got nine in Swaheli.”
“You mean,” I said, “that they can only count as far as eight?”
“Oh, no,” he said quickly. “They have got ten, eleven, twelve, and so on. But they have not got nine.”
“Does that work?” I asked, wondering. “What do they do when they come to nineteen?”
“They have not got nineteen either,” he said, blushing, but very firm, “nor ninety, nor nine hundred”—for these words in Swaheli are constructed out of the number nine,—“But apart from that they have got all our numbers.”
The idea of this system for a long time gave me much to think of, and for some reason a great pleasure. Here, I thought, was a people who have got originality of mind, and courage to break with the pedantry of the numeral series.
One, two and three are the only three sequential prime numbers, I thought, so may eight and ten be the only sequential even numbers: People might try to prove the existence of the number of nine by arguing that it should be possible to multiply the number of three with itself. But why should it be so? If the number of two has got no square root, the number of three may just as well be without a square number. If you work out the sum of digits of a number until you reduce it to a single figure, it makes no difference to the results if you have got the number of nine, or any multiple of nine, in it from the beginning, so that here nine may really be said to be non-existent, and that, I thought, spoke for the Swaheli system.
It happened that I had at that time a houseboy, Zacharia, who had lost the fourth finger of his left hand. Perhaps, I thought, this is a common thing with Natives, and is done to facilitate their arithmetic to them, when they are counting upon their fingers.
When I began to develop my ideas to other people, I was stopped, and enlightened. Yet I have still got the feeling that there exists a Native system of numeral characters without the number nine in it, which to them works well and by which you can find out many things.
I have, in this connection, remembered an old Danish clergyman who declared to me that he did not believe that God had created the Eighteenth Century.