Usa "plumbago" in una frase

1. It is said that the essential oils of plumbago help to improve the glandular swelling,

2. It gives the usual greenish trace on white pottery, while a line drawn parallel on the same basis, by a piece of plumbago or black-lead, is black; this being (as pointed out by Brongniart) the easiest criterion, by which to distinguish between molybdena and plumbago, or black-lead

3. —In Cornwall, Litchfield county, Connecticut, plumbago is found, of a good quality, and in considerable masses, in a vein contained in a rock of gneiss, or mica-slate