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.
Many of these maples turn red, orange, or yellow colors in the fall. Next season offers more trees, new items, so keep the Catalog bookmarked... The Sugar Maple tree, Red Maple tree, and Silver Maple trees are the better know shade trees. The Sugar Maple will turn yellow in the fall, and of course is the tree that produces the Maple Syrup. The Silver Maple tree will start off yellow, sometimes with shades of orange or red, but then turns brown before the leaves drop. The Silver Maple tree is still a very pretty tree.