100 YEARS AGO

The old East Anglian proverb, “As blue as wad,” occurs to one visiting the Woad Mill described by Mr. [Francis] Darwin in Nature, in 1896 (vol. v. p. 36) as evidence that woad once yielded a blue dye. As a natural sequence one wonders what sort of blue it was and how it was obtained. A somewhat extended series of inquiries amongst those engaged in the woad industry, amongst those who have written on woad, and amongst botanical, archaeological and chemical friends, failed for a long time to elicit the desired information. Curious as it may appear, an appeal to botanical and chemical works, to dictionaries and encyclopaedias was equally unsuccessful. The last-named were pretty uniform in their statements about woad, in that it “was formerly used for dyeing blue, but is now superseded by indigo.” Many of the books give an account of the woad-vat in which the manufactured woad is used with bran and lime as a ferment to change the insoluble indigo-blue onto the soluble indigo-white; but they give no clue as to how woad may be used as a blue dye alone. It has been said that the blueness of woad was more or less a myth, and even if it ever possessed this quality it has long since been lost by continued cultivation.

From Nature 1 February 1900.

50 YEARS AGO

Eighty years ago, Jevons, then professor of logic at Owens College (now the University of Manchester), built a machine which could perform logical inference by mechanical means. Other similar machines have been built since then. With the present interest in electrical and electronic computing machines, it seemed worth while to construct a logical machine using modern electrical methods, at the same time basing it on the present-day logical technique of truth tables rather more explicitly than had been done by Jevons… It is not to be expected that a machine of this small size will be able to solve logical problems which could not be done with pencil and paper, but it is hoped that this machine may prove to be of value in the teaching of symbolic logic, and that it will stimulate the interest of students in what otherwise tends to become a rather dull subject, and impress on them the mechanical nature of logical operations.

From Nature 4 February 1950.