In warm weather it is necessary to put the bowl on ice while making it. Put one or two yolks of fresh eggs in a bowl with a small pinch of salt; commence stirring with a box-wood spoon, or, what is still better, a stone or marble pestle. Stir without interruption, always in the same way and describing a circle. It is more easily done if the bowl is held steady. After having stirred about half a minute, commence pouring the oil in, drop by drop, and as soon as you see that it is thickening pretty well, add also a few drops of vinegar and same of lemon-juice; then continue with the oil in the same way. Every time that it becomes too thick, add a little vinegar, but continue stirring. You put as much oil as you please; two bottles of oil might be used and it would still be thick. Spread it on chicken salad, etc.