Another trio of expertly devised activity books from the Boston Children's Museum. Again, the simple experiments are not step-by-step assignments but suggested solutions or responses to questions that come up in process. . . . Baking Chemistry, the simplest of the three, begins with baking a small cake and discovering what happens if certain ingredients are left out, then goes on--by way of explaining the results--to investigate and compare the effects of two of the ingredients, baking soda and baking powder. A simple bread recipe introduces yeast and its comparable effect, which leads into ways of measuring and identifying the gas released. In the same way Drinking Straw Construction first shows the wooden framework of a real house under construction, then--cautioning that the real thing wouldn't necessarily behave in the same way--leads children to think out ways of making rigid frames, and experiment with different shapes, using drinking straws and then broomsticks or wooden dowels. . . . Water Pumps and Siphons, the most technical of the three, prods readers to ask questions and discover answers about the workings of a simple suction tube, then more sophisticated siphoning devices and simple pumps. On the way, Zubrowski points out how these devices illustrate the principles behind the first thermometer, a type of fire extinguisher, and precursors of the steam engine. Exemplary.