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.
Staff Forester. The leaves of most trees should be green, but sometimes in the Great Plains, tree leaves turn from green to yellow. Itâs. a problem called chlorosis. Chlorosis is an abiotic (not caused by a living organism such as a fungus or virus) disease. Itâs characterized by the greenish-yellow to yellow leaves.