Account-keeping.You wonder, perhaps, that people did not have books to keep their accounts in, as we do; but in early days people’s books were made of clay, and were more like our slates, and they scratched on them with a sharp instrument called a stylus, which looks something like our stylograph, but had no ink inside, and they could not put these in their pockets.
Modern arithmetic.It was not till the beginning of the third century before Christ, that the Greek Archimedes proposed a plan not altogether unlike ours, because he was a very clever scientific man, and he wanted to do difficult sums, which he could not with the old Greek system. And something of the kind was used in India. But it was not introduced into Europe until about 1000 years after Christ by the Arabs, who had made many conquests. The first English book about it seems to have been written in the reign of Edward III. Chaucer, who died in 1400, talks of the “figures newe,” i.e., the figures we use now, instead of those difficult Roman characters which we find in the Bible.
But I think that before that, people had begun to use some such plan as ours. Have you ever heard of public-houses being called “The Chequers,” and seen a painted board hung up covered with squares of different colours? This was once a sign for a house of public entertainment, where people could make reckonings, and the place where they reckoned the money they paid was called a “counter,” and the court belonging to the king where the people paid their taxes was called the Court of Exchequer.
Suppose a man came into an inn, he would find the counter marked with lines thus:—
| Score. | Dozen. | One. |
and he could have say 3 glasses of beer; the landlord would put a chalk mark for each, but when he had had 12, one mark would be put instead in the next row, or in the third row if he had had a score, i.e., 20, and these marks would correspond with pieces of money. Thus we have pence and shillings and pounds, and we put dots between instead of lines to mark them off.
Here we will take real pieces of money. Suppose £1 „ 14 „ 6 has to be added to S.7 „ D.9. I say 9 and 6 make 15 pence. I change the 12 pence into one silver shilling, add that to the 14 shillings and the 7, and I get 22 shillings. 20 shillings is one pound, so I change that and leave the 2 shillings. Thus I get altogether £2 „ 2 „ 3. We can now write that in figures and add, as before. Suppose I had to pay to A £1 „ 17 „ 9, and I had £2 „ 14 „ 6. We can first do the sum with real money. I find I have not enough pence to give 9, so I have to change one of the shillings, then I shall have 18 pence, out of which I give 9, and write down 9 left. Now, I have only 13 shillings, and I want to pay 17, so I change one pound, then I have 33 shillings, out of which I take 17 and have 16 left. When I have given the pound, I have none left, and there remains in my purse S.16 „ D.9. We can then also write it down thus—
| £ | S. | D. | ||
|---|---|---|---|---|
| 2 | „ | 14 | „ | 6 |
| 1 | „ | 17 | „ | 9 |
| 16 | „ | 9 | ||
putting the money we have to take away below, pounds under the pounds, shillings under shillings, etc.
Decimals.After a while people all agreed to have for general arithmetic what we call the decimal notation, or reckoning by tens, and so lines were drawn, and figures in the first row were worth one, in the second ten, in the third ten tens, i.e., 100; after that would come figures representing ten hundreds or a thousand, and then ten thousands, and then a hundred thousands; and so we could go on to any length. Ten seemed such a natural number to use, because we all have our ready-reckoner in our ten fingers.