These latest additions to Asimov's science-history series don't explain their scientific subjects with any flair or special care. Rather, his historical approach sees him, in the volcano book, ticking off major eruptions from Thera in Cretan times to Mt. St. Helens in 1980; and, in the solar book, describing gadgets and devices from an experimental paraboloid mirror to focus sunlight, devised in 230 B.C. This latter survey, which leads up to solar cells, is better integrated with explanations than is the volcano history, but still cursory; and as for future possibilities of solar power, Asimov ignores all small-scale and local uses of wind, tide, and so on, and discusses only the "hundreds of billions of dollars" project of lining up enormous areas of solar cells in space. Both books contain the odd interesting item, but Solar Power has at best a skimpy utility and Volcanoes less.