50. And the Earl of Halifax has often informed me of the great Benefit they found by the Use of Ventilators, in several Nova Scotia Transport-Ships, twelve to one more have been found to die in unventilated than in ventilated Ships. It is indeed a self-evident Thing, that the changing the foul Air frequently in Ships, in which there are many Persons, will be a means of keeping them in better Health than not doing it; which makes it the more astonishing that effectual Proposals to remedy so great an Evil, should be received with so much Coldness and Indifference by Mankind. They little consider that it is the high Degree of Putrefaction (that most subtile Dissolvent in Nature) which a foul Air acquires in long stagnating, which gives it that pestilential Quality, which causes what is called the Goal-Distemper. And a very small Quantity, or even Vapour of this highly attenuated Venom, like the Infection or Inoculation for the Small-pox, soon spreads its deadly Infection. Ought not Men therefore, from the common natural Principle of Self-Preservation, to use their utmost Endeavours to shun this pestilent Destroyer, by which Millions of Mankind have perished in Ships?
An Account of some Tryals to cure the ill Taste of Milk, which is occasioned by the Food of Cows, either from Turnips, Cabbages, or autumnal Leaves, &c. Also to sweeten Stinking-water, &c.
51. This Method of blowing Showers of Air up thro’ Liquors, will be of considerable Use in several other Respects, as well as in Distillation, as appears by the following Trials, viz.
52. I have been informed that it is a common Practice, to cure the ill Taste of Cream from the Food of Cows, by setting it in broad Pans over hot Embers or Charcoal, and continually stirring it, till scalding hot, and till cool again: But when I attempted to do this much sooner, and more effectually, by blowing Showers of Air up thro’ it; I soon found it to be impracticable, by reason of its very great Degree of frothing up. The ill Taste must therefore be got out of the Milk, before it is set for Cream; which I have been told, has been practiced, and that with some benefit, by giving the Milk a scalding Heat, without stirring it.
53. May 22. I ventilated some ill tasted, new unheated Milk of a Cow which was purposely fed with Crow-Garlick mixed with cut Grass. After 15 Minutes Ventilation the Taste was a little mended; in half an Hour’s blowing it was something better. At the Hour’s end it had the same Taste, but was sensibly better than the unventilated Milk. I was disappointed of an Opportunity to repeat the Experiment with Crow Garlick Milk, with a scalding Heat; it would then probably have been soon perfectly cured; as it is reasonable to believe from the Event of the following Experiments, viz.
54. August 23, four Quarts of ill tasted new Milk, from a Cow which had fed eighty-four Hours on Cabbage Leaves only, and drank during that Time very little Water; were put into a leaden Vessel, eight Inches in Diameter, and thirty Inches ches deep. The leaden Vessel was heated in a large Boiler, and set into a Vessel of hot Water; thereby to give the Milk a scalding Heat, and also keep it hot. In ten Minutes Ventilation it was perfectly cured of its ill Taste; and after standing twenty-four Hours in a broad Pan, there was a thick Scum which was half Cream and half Butter, free from any ill Taste; the skimmed Milk was not sheer or thin: So here is a Method to make good Butter from ill tasted Milk.
55. The Froth of the Milk was so great, by reason of a too brisk Ventilation, as to make it froth over the Vessel, which was thirty Inches deep; if it had not been kept down, by constantly lading and breaking the very large Bubbles of Froth. But when the Ventilation is more gentle, the Froth has risen but three Inches from six Quarts of Milk, which was nine Inches deep. The Cabbage Milk was but six Inches deep. I repeated the like Operation the same Day, with the Evening Milk of the same Cow; but giving it only a Heat, that I could bear my Fingers in, for a little Time; with this Degree of Heat, after forty-five Minutes Ventilation, the Milk (tho’ much better tasted) yet was not so compleatly cured, as the former Milk. Hence we see, how necessary Heat is, to volatilize the rancid Oyl (which gives the ill Taste) to such a Degree as to cause it to fly off by Ventilation.
56. It was observed that what was milked from this Cow a Week after she had done eating the Cabbage, had an ill Taste.
57. I have not as yet had an Opportunity, to try to cure, in the same Manner, the ill Taste of Milk, which is occasioned by Cows feeding on autumnal Leaves, or Turnips, they having probably eaten this Autumn, the fewer Leaves, on account of the Plenty of Grass, occasioned by much Rain; which has also hitherto prevented Turnips from being rancid, which are observed to be most so, when they shoot out in the Spring. As Opportunities offer I purpose to make Trials, which I conclude others will also do, which will probably be attended with the same good Effects as that on the Cabbage Milk.
58. But tho’ the ill Taste of Milk from feeding on Cabbage Leaves, was thus effectually cured by volatilizing with Heat, and dissipating by Ventilation the rancid Oil; yet the bitter Taste of a strong Infusion of Chamomel Flowers in six Quarts of Water, was not sensibly abated by an Hour’s Ventilation of it, while scalding hot.