An account of a useful discovery to distill double the usual quantity of sea-water, by blowing showers of air up through the distilling liquor

by Stephen Hales

59. I am informed that, in Devonshire, they set the Pans of Milk on Trivets, making Fires under them, to give the Milk, gently and gradually a scalding, but not a boiling Heat, which would disturb the rising Cream; and then set it on the Floor in the Milk-house to cool, where in twelve Hours it has a thick Scum, partly Butter and partly Cream: The skimmed Milk is very thin and sheer; and the Cream in great Plenty and delicious, except it gets a smoky Taste, which it is apt to do; and which might probably be prevented, by having a Range of as many Stoves, as there are Pans of Milk to be used at one Time; all to be warmed by one Fire, either at one end, or the middle of the Flue or Funnel in the Brick-work, which conveys the Smoke and Heat under the Stoves. And as the Pans nearest to the Fire will soonest have their due Heat, on their Removal to bring the farthest and coolest Pans nearest the Fire; and instantly covering the uncovered Stoves with proper Covers to prevent the Heat and Smoke from coming out; by this Means the Milk would all be soon heated, with any kind of Fuel, and that with much less in Quantity than in the common Way.

60. And the more effectually to prevent the Smoke from coming at the Milk, it may be well to have the broad outer Rim of the Pans turned perpendicularly downwards, three or four Inches, that it may enter deep into a circular Groove of Sand; and if it shall be needful the Sand may be wetted in order the more effectually to prevent the Passage of the Smoke: I thought of this Method about fifty Years since on tasting the smoky Butter in Somersetshire. By the same Means the Poor might save much Fuel in boiling the Pot, especially in Summer, when a Fire is wanted only for boiling the Pot.

61. When any Pans are to be removed from the Stoves, the Ascent of the Smoke thro’ the uncovered Stove, may be prevented by first closing the Flue near the Fire, by an Iron Sliding-shutter or Register.

62. Milk might thus most commodiously be heated to a scalding Heat with little Fuel, fit for Ventilation, in a Vessel of a proper Depth, set in the same Manner as the Pans in a Stove, to secure it from Smoke, with Bellows fixed properly near it: (see Fig. 3.) By this Means there would be little Trouble or Expence in curing ill tasted Milk by Ventilation.

63. May 14th, meerly to see what the Event would be, a Gallon of new Milk, just from the Cow was ventilated, for an Hour and half, which produced six Ounces of Butter; and tho’ it was ventilated half an Hour longer, yet no more Butter was made; it was whitish, wanting both the Colour and Taste of good fresh Butter.

64. I am credibly informed, that in the Places famous for making the best fresh Winter Butter, they set the Pot of Cream in warm Water, so long as till it has acquired that small Degree of Sourness, which it very soon has in warm Summer Weather, which gives it its agreeable Flavour. And in order to give it Colour, they grate a well coloured Carrot into a little Milk, which as soon as stained, is strained from the Carrot thro’ a Sive, and then mixed with the Cream.

65. It is found by Experience, that the Quantity of Cream is increased, by putting into the Milk a little warm Water in Winter, and cold in Summer; which being thereby, in some Degree thinned, the Cream is thereby more easily disintangled, so as more freely to ascend to the Surface of the Milk.

66. I ventilated three Gallons of stinking Jessops-well purging Water. On first blowing, the Smell of the ascending Vapour was very offensive, which Offensiveness abated much in five Minutes: In eleven Minutes the Smell was much better: In twenty Minutes the Water seemed sweet both in Smell and Taste; and not sweeter at the End of forty-five Minutes, fifteen or twenty Minutes will probably suffice.

67. July 20th three Gallons of stinking Sea-water were ventilated; in five Minutes it was much sweetened, and no ill Smell in the ascending Air, tho’ at first it was very offensive: At the End of ten Minutes it had a small Degree of ill Taste; after twenty Minutes no ill Taste or Smell. It frothed near a Foot high during Part of the Ventilation; this from the Bitumen, &c.

68. Some Sea-water which was made to stink with Flesh and Isinglass being put into it, was not made perfectly sweet, not even by a ventilated Distillation, and an Hour’s more Ventilation after it was distilled; so that Putrefaction with animal Substances, is not easily compleatly cured by Ventilation.