With their speed of look-up and potential for effortless cross-referencing, CD-Roms offer the ideal format for an encyclopedia. This one gives four look-up options - by time, topic, place or simple alphabetical. Take any year from 2 million BC to the present day and you can find out quickly what were the innovations of that period. However, it is only when you have begun the search that this product shows its real character.

Starting, at random, with "corkscrew", where I learnt that the cork first appeared in 1530 and corks and corkscrews were widespread by the 17th century, I was led, by the "related topics" switch, to screws (invented around 300 BC), nuts and bolts (first referred to in 1611) and nails (invented around 3000 BC).

From "ballpoint", invented by John H Loud in the 1880 but only perfected by Laszlo (which this disc misspells by omitting the "s") Biro in 1938, I discovered that ink was known to the Egyptians in 3200 BC, though the quill pen did not hit Europe until around AD 600. In 1809, Joseph Bramah devised a machine to cut many nibs from one feather, and the road was open for Lewis Waterman to invent the modern fountain pen (after losing a sale through using a leaky version) in 1884.

The entries are well written to fit the screen, with basic details and occasional useful additions of peripheral material. Altogether, it offers splendid prospects for the casual browser, who will find it difficult to resist the temptation to continue rambling through progressively more tenuously related topics.

With only 600 discoveries and inventions covered in all, however, the serious researcher would do better to buy a book. And they really ought not to have misspelt "millennium" (with one "n") on the front of the instructions.

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