The publication of this book is extremely timely, for the next major advances in manned space flight after Project Apollo will most likely be made in earth orbital operations. Manned exploration of the moon will certainly continue after the initial landing, but it will be performed essentially with the Saturn V launch vehicles and Apollo spacecraft developed in Apollo, especially in the early phases. Modifications to this basic hardware will increase operating capabilities to permit extensive lunar explo ration during prolonged stay times by the astronauts on the moon's surface. Manned orbital space stations have been studied for years, and NASA is already well along in development of its first attempt to provide more spacious accommo dations for astronaut-scientists in its Saturn Workshop program. While the Workshop is certainly not the ultimate space station of which our technology is capable, it is a workable, poor man's approach to the immediate need for using and expanding our present manned space flight capability without a de trimentalloss of momentum. The approach of converting a Saturn rocket stage into a manned laboratory and observatory in space is an improvisation that matches the use of the jerry-built Jupiter C back in 1958 to launch Explorer I. Let's hope that it can get the job done just as effectively.

The publication of this book is extremely timely, for the next major advances in manned space flight after Project Apollo will most likely be made in earth orbital operations. Manned exploration of the moon will certainly continue after the initial landing, but it will be performed essentially with the Saturn V launch vehicles and Apollo spacecraft developed in Apollo, especially in the early phases. Modifications to this basic hardware will increase operating capabilities to permit extensive lunar explo ration during prolonged stay times by the astronauts on the moon's surface. Manned orbital space stations have been studied for years, and NASA is already well along in development of its first attempt to provide more spacious accommo dations for astronaut-scientists in its Saturn Workshop program. While the Workshop is certainly not the ultimate space station of which our technology is capable, it is a workable, poor man's approach to the immediate need for using and expanding our present manned space flight capability without a de trimentalloss of momentum. The approach of converting a Saturn rocket stage into a manned laboratory and observatory in space is an improvisation that matches the use of the jerry-built Jupiter C back in 1958 to launch Explorer I. Let's hope that it can get the job done just as effectively."

We know a great deal about historical climate and its variations from various geo logical studies. There are two points worth remarking on. One is that the climate changes frequently and radically, but that the degree of variation and even sense of variation depends on the time scale which we are considering. Secondly, that this is a most unusual geological period for the Planet Earth; we are living in a period of mountain building and glaciations, whereas during most of the last 250 million years (m.y.) there was little ice and little topography. A good view of climate change of the last hundred m.y. can be gained by looking at the paper of Kellogg. We are now in a period of extensive glaciations. The previous interval occurred 300 to 250 m.y. ago, when even the Sahara was glaciated. (Of course, it was at that time near the position of the South Pole; we know that 300 m.y. ago the continents had not broken apart and formed one land mass.) Apparently between 250 and 20 m.y. ago there was little ice on the Earth, even at Antarctica. Continental basins were flooded by shallow seas. This was the period when plant life and marine life proliferated and when most of our fossil fuels were laid down."