The following remedies have been wed with varying success to prevent incrustation: -

1. Potatoes, 1/80 th of weight of water prevents adherence of scale.

2. 12 parts salt, 2 1/2 caustic soda, 1/8 extract of oak bark, 1/2 potash.

3. Pieces of oak-wood suspended in boiler and renewed monthly.

4. 2 oz. muriate of ammonia in boiler twice a week.

5. A coating 3 parts of black-lead, 18 tallow, applied hot to the inside of the boiler every few weeks.

6. 12 1/2 lb. of molasses fed into an 8-horse boiler at intervals, prevented incrustation for six months.

7. Mahogany or oak sawdust in small quantities. Use this with caution, as the tannic acid attacks ipon.

8. Carbonate of soda.

9. Slippery elm bark. 10. Chloride of tin.

11. Spent tanners' bark.

12. Frequent blowing off.

13. Method adopted by Schubler. It is liquid carbonic acid, which he brings in a bomb in connection with the boiler, which, though cold, is still filled with water. The water hereby becomes saturated with carbonic acid. This carbonated water then dissolves the carbonate of lime, the principal part of the incrustation, and forms an acetous carbonate of lime, which falls off, and, after removal of the water, the boiler will be found free from the incrustation. (See also ii. 42.)