Asimov begins with a lovely lecture on logarithms, of all things, an enchanting bit about the obsolescence of the slide rule and the usefulness of exponential additions and subtractions to the growing needs of a calculating astronomy and physics. The premise that we will go on with this kind of numerical lore from one sort of infinity to another is continued in the next several essays--describing the search for absolute zero and the chilling of gases down to a point very close to the complete cessation of molecular activity. This last excursion leads in turn to essays on earthly exploration and the quest for the ends of the earth--east and west and north and south--culminating in the conquest of the South Pole. But, alas, the lore of limits then changes into more typical Asimovian jaunts into space and the planets, conjectures on moons, asteroids, and meteorites, with a particular focus on the moons of Mars and the possible existence of a binary partner of our sun. Standard facts and figures, these; deductions and speculations which do not scintillate. Even the final essays on life Out There are familiar, via Asimov's recent Extraterrestrial Civilizations (p. 606), while a wind-up on the difference between life and death seems a typical rationalist approach defining life as organization and death as entropy. Still, it's worth the price for those fans who didn't see the pieces individually in The Magazine of Fantasy and Science Fiction-and there's the bonus of an index to all 238 Asimov essays which have appeared between those covers.