In making a model of a small tract of country showing, on a large scale, the intersection of road and railway, modelling clay may be used if the model is to be somewhat rough in its nature, is required for a temporary purpose only, and is to be used within a short distance of the place where it is made. The drawbacks to the use of modelling clay are its want of permanency, the difficulty of moving the finished model, and the absence from it of the natural colours of the objects represented; the advantages are facility of execution and cheapness. If the model is to be of a more or less permanent character, or if it has to be moved about from place to place, the structure may be built up of wood and plaster of-Paris; these materials can be painted to indicate the natural colours of the objects represented. If a auantlty of small detail has to be clearly shown, modelling wax may be recommended. This wax is of a soft and plastic nature, and remains permanently so, thus forming an excellent substitute for wet clay; it must, of course, be protected from rough usage; modelling wax is supplied in various colours.

Another material that may be used is plasticine, which is an imitation of modelling wax, but is only made in one colour (a greenish grey); plasticine is quite as pleasant to handle, and retains its plasticity in the same manner as wax. The ordinary method of constructing a model is as follows. Surround the required surface area with a wooden frame, making the frame rather deeper than the probable thickness of the intended model. The frame will present the appearance of a shallow wooden box, for which a cover either of wood or glass, as may appear most desirable, may be constructed. The bottom of the box must be of a substantial character, and should be stiffened with cross-pieces or battens; handles should also be provided and firmly connected with the bottom or foundation board. The sides of the box may be of 1/2-in. stuff. In this box the clay is placed and worked roughly to shape, and is then trimmed carefully with spatulas and modelling tools. Grass may be indicated by powdered moss sprinkled on a coating of glue, and cinders, etc., by painting the place with Indian ink; railings, bridges, buildings, and structures of that kind can be formed of timber stuck into the clay.

When a model is made of plaster-of-Paris the elevated portions of the structure are usually filled with "hollows," which are rough boxes made of 1/2-in. stuff sprigged together and fastened to the foundation board. On these hollows, which greatly lessen the weight of a model, the plaster is laid with a spatula or small trowel, and is worked as nearly as possible to the form required. Bridges should be fashioned in timber and fixed in position before anything else is done. Buildings may be cut out of wood and fastened down with wire nails, which should be long enough to reach the foundation board. The railway metals may be made of strips of wood. Plaster-of-Paris mixed with water sets in about nine or ten minutes; if that time is not long enough for shaping the contour of the model, the setting of the plaster may be retarded for a further ten minutes by mixing white of egg with the water (5 per cent, of white of egg to 95 per cent, of water). Errors in construction, however, are easily corrected after the plaster has set. Surplus material is readily removed with a joiner's chisel and a light mallet, and additions may be made by roughening the surface of the plaster, well wetting it, and adding as much fresh plaster as is necessary.

The model may then be painted either in oil or in water colours. Railings, signal posts, etc., may be let into holes drilled in the plaster. For trees, those supplied in a box of children's toys may be employed.