If the boiler be stationary, and fed with fresh water, the amount of anti-petrify-ing mixture per horse power for 336 hours' consumption may bo made by mixing together 12 oz. muriate of soda, 2 drs. of dry tannic or gallic acid, 2½ oz. of hydrate of soda, or 1 or ½ oz. of sub-carbonate of potash. For locomotive boilers travelling an average of 140 miles per day, the quantity of the mixture per bone power is increased one-fifth. If the water be brackish, or a mixture of salt and fresh, the muriate of soda is omitted, and instead of 12 oz., are used for 2½ oz. of hydrate of soda, and 5 drs. instead of 2 of the dry tannic or gallic extract. The mixture is also prepared in this manner when sea water is used in the boiler. The patentee prefers introducing the mixture into stationary boilers in quantities for two, three, or more days, but locomotive and marine boilers are to be supplied daily with a portion of the mixture, corresponding with the amount of duty to be performed.