The first American publication of a thirty-odd year old portrait of Erasmus Darwin, grandfather of the famous Charles and great (three times) grandfather of author Pearson, the last probably accounting not only for the intimacies involved but also the reverence indulged in. Darwin was 18th century England's physician par cellence (George III wanted him but didn't get him; Darwin was too democratic); he was also a philosopher, a poet, and head mandarin of the Lunar Society, whose celebrated enclave held Watt (of the steam engine), Wedgwood (of pots), and Priestley (of oxygen). Darwin was a stutterer who looked twice his age; nevertheless his sallies never missed nor was his sexual appetite ever starved. Twice married and many more times a father, his home was a happy one; a failing though- grumpy disapproval of all things spiritual- cost him a son, a wistful lad who ended it all at the bottom of the River Derwent. Pearson's style here- it has changed since then- is pretty much drawing-room English, comfortably ensconced with wit and stage-bearded with wisdom. The hyperbole of course gets heavy-handed: was Darwin really the progenitor of eugenics, irplanes, submarines, psychoanalysis? That he was the ""parent of Creative Evolution"" one can doubt, a doctrine made unfashionable, ironically enough, by his grandson. Put it all down as a bunched-together biography- incidents, anecdotes, character studies-which in its fustily fastidious way is fascinating. And if Darwin as a personality doesn't emerge as engaging as he was intellectually extraordinary, well one can't have everything, especially all in one family.