Skiddaw Slate (as opposed to Honister slate which has a green hue) and is used for building, in the Lake District. The traditional buildings of Keswick and other settlements are almost entirely of Skiddaw slate. The slate is also used for making souvenirs, monuments, ornaments etc. Smaller fragments are used for gravels or for ornamental pathways. Skiddaw Slate Skiddaw slate is an early Ordovician metamorphosed sedimentary rock, as first identified on the slopes of Skiddaw in the English Lake District. The base of this series is unknown. The thickness could, therefore, amount to several thousand feet of sediment. These sediments were formed
Change of variables (PDE) Change of variables (PDE) Often a partial differential equation can be reduced to a simpler form with a known solution by a suitable change of variables. The article discusses change of variable for PDEs below in two ways: For example, the following simplified form of the Black–Scholes PDE is reducible to the heat equation by the change of variables: in these steps: Advice on the application of change of variable to PDEs is given by mathematician J. Michael Steele: Suppose that we have a function formula_24 and a change of variables formula_25 such that there exist functions formula_26 such that