For great magnification or reduction a lens of comparatively short focus must be used, but, as a long-focus lens gives a more perfect image, we use one of very long focus--thirty-six inches--for copying the same size or for slight magnification or reduction." "Are you going to magnify these cheques ?" Mr.Britton asked.
"Not in the first place," replied Thorndyke.

"For convenience and speed I am going to photograph them half-size, so that six cheques will go on one whole plate.

Afterwards we can enlarge from the negatives as much as we like.

But we should probably enlarge only the signatures in any case." The precious bag was now opened and the twenty-three cheques brought out and laid on the bench in a consecutive series in the order of their dates.

They were then fixed by tapes--to avoid making pin-holes in them--in batches of six to small drawing boards, each batch being so arranged that the signatures were towards the middle.