A matrix of wood or iron is covered with successive layers of papers, pasted together so as to form pasteboard.
The Montana sapphires and the matrix have been described by Dr G.
If the matrix, however, is originally crystalline it does not seem probable that perlitic structure can develop in it.
When mixed the concrete is carried at once to the position required, and if the matrix is quick-setting Portland cement this operation must not be delayed.
As, in succeeding members of this same series of cast irons, more of the graphite of the initial skeleton changes into cementite and thereby becomes part of the metallic matrix, so the graphite skeleton becomes progressively thinner and more discontinuous, and the matrix richer in cementite and hence in carbon and hence equivalent first to higher and higher carbon steel, such as tool steel of I carbon, file steel of 1.50%, wire-die steel of 2% carbon and then to white cast iron, which consists essentially of much cementite with little ferrite.