188.—To boil Sugar by the Thermometer.
All the foregoing tests are according to the old style of boiling; but a boiling-glass can now be had which enables us to boil to a better degree of accuracy. Thus, to boil to the pearl is to boil to 220 degrees; the small thread 228 degrees; the large thread 236 degrees; the blow 240 degrees; the feather 242 degrees; the small ball 244 degrees; the large ball 250 degrees; the small crack 261 degrees; the hard crack 281 degrees; the caramel 360 degrees.