mercurial compounds. These Yantras are known by the names of Damaru, Urdhvanalika, Valuka, Bhudhara, Dola, Patala, Nabhi and many others. For diagrams of some of them, see Plates I. -VI. Like other minerals mercury should be purified for medicinal purposes. This can be done in various ways. Sharngdhara gives the following directions : — Rub mustard seeds and garlic together until reduced to the consistency of mud. Make two small cups of the mass. Put mercury in one of them, lute the other over it, and dry it in the sun. Tie the vessel in a piece of cloth, suspend it for three days in an earthen pot filled with Kanjika and place it on the fire. Take out the mercury from the vessel and rub it for one day in Ghritakumari juice, another day in a decoction of Chitraka (Plumbago zeylanica), for the third day in that of Kakamachi (Cocculus indica), and the fourth day in that of the three Myrobalans. Wash the mass in Kanjika, to separate the mercury from it. Again put the quicksilver in a mortar containing half its quantity of bay salt, and triturate it for a whole day. Add an equal quantity of mustard seed, and rub the mass in a rice-husk decoction. Repeat the whole process with garlic and then with sal-am-
