Pat Shingleton: "Rittenhouse and... the Divining Rod..."
As wood swells and shrinks it gains or loses water once it is at or below a 30% saturation point. In the "deep south," elevated measures of humidity cause the shrinking and changing shapes of indoor wood. Examples include gaps between floorboards, creaking stairs, trim joints opening up, piano sound boards changing tunes and doors and drawers that once stuck, opening easily. Of course the process reverses when higher levels of relative humidity restores moisture content to its original levels. David Rittenhouse made mathematical instruments for surveying and astronomy and in the 1700s invented the Rittenhouse Hygrometer. This weather instrument registers the relative humidity of the air by using wood as its sensor. Wood swells and shrinks about 80 times as much around the growth rings and 40 times as much across the rings. Rittenhouse took two identically sized strips of mahogany, glued them together to complete a single slat and attached one end to a base while placing a tipped pointer on the other end. When the humidity rose, the strip swelled, forcing the slat to bend and when it dropped the strip shrank and bent. Rittenhouse’s invention is used today by designers of plywood, laminated floors and layered wood to ensure that these products remain flat as they adjust to the power of relative humidity. The weather stick was invented in the late 1700s and is still used to forecast the weather. Referencing "sticks," attempts to locate water were called dowsing and a dowsing rod, divining rod or witching rod was used. The rod was a Y shaped twig that supposedly jumped when above ground contact with a water source occurred. My grandfather embraced this process and would whittle the rod to educate us as to its benefits. Not that interested, we would use the rods as “apple launchers.” Jamming an apple on the rod and whipping it like a fishing rod would propel the apple. My brother Kevin holds the record for hitting two heads with one apple from a “launcher.” Kevin first hit Pumpkin Head Hulick and the apple ricocheted into Bob “Head” Krestel.