This book reprints my Mathematical (James columns from the 1978 and 1979 issues of Scientific American Magazine. It is the fourteenth such collection, and I have one more to go before running out of columns. As in previous anthologies, addenda to the chapters update the material with information supplied by faithful readers, and by papers published after the columns were written. In two cases — a column on pi and poetry, and one on minimal sculpture — there was so much to add that I have written new chapters which appear here for the first time.