PART II

I. Some Practical Advice 271 The inventor, ancient and modern--Barriers to mechanical progress in the past--Laws of gravitation--How to adjust sewing machines.

II. Mechanical Movements 306 Coffee mills--Pulleys--Pumps--Pistons--Levers--Steam engine and water wheel governors, etc.

III. The Weather and Indoor Work 349 How to make a rain gauge--Hail--Snow--Designing, making and inflating paper balloons--Magnetized watches--A boy's wheelbarrow--Vacuum cleaners.

IV. Motors and Typewriters 387 Motors, gasolene and steam--Automobile frames--The modern typewriter--Directions for securing copyrights.

ILLUSTRATIONS

A Motor-Boat Model _Frontispiece_

FACING PAGE

Boat-House and Workshop 42 The Creek 70 Making a Motor Launch 88 Finishing the Motor Launch 112 The Monoplane Model Complete 160 Making an Aeroplane Model 180 Making Kites 190 A Sundial Made of Concrete 208