Caper Sauce

Set into a saucepan two ounces of butter, mix it with one and a half ounces of flour; beat the flour and butter well together with a spoon, so as to obtain a smooth paste; now moisten it with two gills of water, add a pinch of salt, stir the liquid on the fire until the sauce becomes thick. At the first boil, remove it to the side of the range. It should be somewhat more consistent than thin. Incorporate into it gradually, two ounces of butter divided into small pats, the sauce should now be creamy; remove it and finish by adding some small nonpareil capers, and the juice of a lemon; then serve.