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.
Brown Fall Color. Many oaks that turn yellow or red in the fall will also exhibit some brown fall color concurrent with other colors, such as the chestnut oakâs yellow and brown fall foliage, or the brownish-red fall color of the red oak.ak trees (Quercus spp.) are either evergreen or deciduous, depending on species. Some oaks, such as the evergreen Coast Live Oak (Quercus agrifolia), hardy to U.S. Department of Agriculture plant hardiness zones 9 and 10, do not lose their leaves in fall.