Preheat the oven to 450 degrees F (220 degrees C).
Line the bottom and sides of a 9 inch pie plate with one of the pie crusts. Brush with some of the beaten egg to keep the dough from becoming soggy later.
Place the sliced peaches in a large bowl, and sprinkle with lemon juice. Mix gently. In a separate bowl, mix together the flour, sugar, cinnamon, nutmeg and salt. Pour over the peaches, and mix gently. Pour into the pie crust, and dot with butter. Cover with the other pie crust, and fold the edges under. Flute the edges to seal or press the edges with the tines of a fork dipped in egg. Brush the remaining egg over the top crust. Cut several slits in the top crust to vent steam.
Bake for 10 minutes in the preheated oven, then reduce the heat to 350 degrees F (175 degrees C) and bake for an additional 30 to 35 minutes, until the crust is brown and the juice begins to bubble through the vents. If the edges brown to fast, cover them with strips of aluminum foil about halfway through baking. Cool before serving. This tastes better warm than hot.