In their annual sessions the various Sections of the Royal Society are accustomed to take up for general discussion a topic of current interest and this gives Fellows and special guests from the natural sciences, the social sciences, and the humanities an opportunity for useful communication across the disciplines on an important subject. In 1961 the topic was an especially vital issue, the population explosion, and this volume, based on the papers given at the meeting, has much valuable information and many pertinent and provocative comments on this phenomenon particularly as it affects Canada. T.W.M. Cameron leads off with a general background on the causes and consequences of the population increase around the world. Then come a group of papers presenting various aspects of the population in Canada’s settled areas. Pierre Dagenais studies the growth in that population in recent years; Guy Rocher presents developments in our labour force in the 1900’s with particular reference to the older age group, to women, and to the unemployed; Jacques Henripin describes ethnic and linguistic patterns over the country; Nathan Keyfitz outlines new patterns in the birth rate and their significance. A.R.M. Lower concludes this portion of the book with a lively historical study of the effects of natural increase and waves of immigration in the French and English periods, leading on to our present “bold experiment” in Canada which assumes the “risks of a non-homogeneous, non-integral society with every value fighting it out for survival.” The second part of the book turns to those largely unsettled areas stretching away in Canada’s north and considers the potentialities of these areas as a more permanent habitat for man. With an introduction by René Pomerleau, various problems of settlement are brought forward. W. Keith Buck and D.J.F. Henderson discuss economic aspects of mineral development in the north; E.W. Humphrys, the possible use of atomic energy as a way of coping with fuel and supply; M.J. Dunbar, the prospects of support for a new population in the use natural resources contributed by the land and the sea; G. Malcolm Brown, problems of man’s acclimatization to life in a colder climate; Trevor Lloyd, the kind of settlement in the Far North which is desirable and possible given its special conditions of subsistence and transportation and economic activity. All these authors stress that any planning for a northern future “must be based on a broad, systematic and thorough scientific appraisal.” This is an important and absorbing book and it will give both specialist and general reader much to think about.