1- Combine sugar, corn syrup, & 1/2 c water in a 2 quart heavy saucepan. Cook & stir over medium-high heat until mixture boils. Clip a candy thermometer to the side of the pan. Reduce heat to medium and continue cooking, without stirring.
2- When thermometer reaches 260, hard-ball stage (10-15 minutes), remove pan from heat and remove thermometer. In a large mixing bowl beat egg whites with an electric mixer on medium speed until stiff peaks form. Gradually pour hot mixture in a thin stream over whites, beating on high speed about 3 minutes; scrape sides of bowl occasionally. Add vanilla. Continue beating on high just until it starts to lose its gloss (5-6 minutes).
3- Drop a spoonful onto waxed paper. If it stays mounded, it has been beaten sufficiently. If mixture flattens, beat 1/2 to 1 minute more. Drop by spoonfuls onto waxed paper.
**This recipe does not turn out well in humid or rainy weather.