de Prony brake dynamometers at a tractor contest in 1910. Schematic of a de Prony brake. The de Prony Brake is a simple device invented by Gaspard de Prony to measure the torque produced by an engine. The term  brake horsepower  is one measurement of power derived from this method of measuring torque. (Power is calculated by multiplying torque by rotational speed .).
Typically tree trunks are thought of as being in various shades of brown. They can have many different colours to them, however.Grey is a common colour in tree trunks, as is green when they're younger. Specific species of trees usually have specific bark colour at specific times of year so you should look up the trees you're interested in if you need more information.ypically tree trunks are thought of as being in various shades of brown. They can have many different colours to them, however.
Mature trees have white bark that peels off in thin layers. The heart-shaped leaves are larger than European birches, averaging 3 x2, and these natives hold their white bark color well. In fall, the leaves of paper birch reliably turn a cheerful yellow color.This tree is especially attractive in clumps, which frequently occur in the wild, and can attain heights of 100.aper birch is a rather short-lived tree (in the tree world, that is) that can live up to 140 years. It has a shallow root system and typically reaches less than 2 feet beneath the soil surface. The deciduous foliage has a high decomposition rate and rapidly forms deep rich soils.