The subject is well handled here in that Mr. Pratt establishes the interrelations between the men and their creations, their times and how the inventions were handled- the intangibles that are often more noteworthy than the products. Going back to the middle ages he states first that explosives, printing and the telescope were responsible for most of the changes the world has undergone since. The follow-through on dynamite exemplifies Mr. Pratt's method. In the West Roger Bacon was the first man known to observe its action, but he did little more than that and it remained for centuries and the work of Sobrero and Schwartz to pass, before Nobel put it to widespread use. Further chapters deal with transportation, gin and reaper, electricity, inventions for the home, building, weapons, and some of the more modern wonders. A healthy internationalism here.