The second item on the list was Australia 6%, and referring to the Daily Mail once more, French saw that Australia 6% was the first item on the second division. This was sufficiently interesting, but when he found that the next five items, Great Western, Associated News, Aerated Bread, Barclay’s Bank, and Alliance Assurance were each the first of their respective divisions, he felt he had stumbled upon something more than a coincidence.
He re-examined the list on this new basis, only to find his conclusions verified. Apparently the person writing it had simply copied down the stocks given in some paper—probably the Daily Mail. In order to obtain variety and to make an unsuspicious-looking list, he had not simply copied them consecutively; he had taken the first out of each division. Then he had gone over the divisions again, using the second name in each case, and so on until he had obtained the whole twenty-five names that he had required. It had not been done with absolute accuracy, but there was no doubt of the general method. From this it followed that any message which the list might convey was contained in the money columns, and French accordingly transferred his attention to the latter.
The amounts extended from 16s. 7d. up to £1039, and varied surprisingly between these extremes. There were none in the £100’s or the £600’s, but all the other hundreds were represented. Speaking broadly, there were more of the £800’s and £900’s than of the lower numbers. But he could not see where any of these facts tended.
There being no obvious line of research, he began a laborious and detailed investigation into the possibilities of substitution, that is, one of those ciphers in which a number or other sign is used to denote a letter. It was clear that single numbers were insufficient for this purpose, as in that case only ten letters of the alphabet could be used. Some combination was therefore involved, and French tried various schemes of addition to meet the case. But though he got three men to assist him in the details of his various tests, he could not find anything which gave the least suggestion of an intelligible combination.
While engaged in this manner, he noticed that so far as the pounds were concerned there were no less than three similar pairs, numbers 2 and 22, 3 and 15, and 10 and 21. He examined these pairs for some time, and then he suddenly made a discovery which seemed to show that at last he was on the right track. He had put the figures down beside each other, so:
| £ | s. | d. | |
| No. 2 | 568 | 5 | 0 |
| No. 22 | 568 | 2 | 3 |
when suddenly he noticed that if the shilling and pence of each item were added the result would be the same: 5+0=5; 2+3=5. Eagerly he turned to the other pairs and wrote them out similarly,
| £ | s. | d. | |
| No. 3 | 1039 | 1 | 3 |
| No. 15 | 1039 | 0 | 4 |
and,
| £ | s. | d. | |
| No. 10 | 748 | 3 | 9 |
| No. 21 | 748 | 5 | 7 |