These sixteen stories, solid if minor, are by the more practised practitioners in the genre -- Brian W. Aldiss, Robert Silverberg, Murray Leinster, Poul Anderson, Isaac Asimov. They include two novel races -- ""sun yachts"" with two mile high sails circumnavigating the earth and hybrid highspeed to-boggans that are a special kind of death trap. Among the adolescents featured is a small genius who whips up a homemade anti-gravity machine among other devices; a witch boy who wants to learn how to make things fly without magic; a logical young scientist in a lively debate with two time travelers; and an isolated youngster afraid to leave the security of ""the Nest"" his father constructed on an icy, sunless world. One of the funniest stories is Robert Silverberg's tale of an artificial cow on the moon and the men who are trying to milk her. A good variety, especially attuned to this age level.