This is another of the labours of a life spent in the service of mankind. One of the most dreadful disasters of a sea-faring state is known to be a want of water. Many attempts have before been made to find a method of making the water of the sea wholesome for the table. For this no kind of filtration is sufficient; for though salt-water may, by passing through some mediums, be freed from all perceptible particles of salt, yet it still retains its bittern4 more nauseous than salt.

Recourse was therefore had to distillation, which performed slowly, produced sweet water, but in so small quantities that water was as easily carried in the ships as fuel. It was therefore necessary to add some ingredient, that might combine the salt, and dispose to a more speedy separation from the water.

For this purpose many substances have been tried, and some of them with sufficient success.

There was still wanting some method of quickning distillation, and this Dr. Hales has at length discovered, and imparted with candour more to be admired than even his sagacity; for he has ingenuously traced it from the first hint, that he may receive no more than his due share of honour from the invention.

We shall exhibit the process of his discovery; for the art of improving hints, and tracing one consequence from another, is of more importance than thea distillation of ten waters. . . .5

The method of blowing air through the boiling water is of such efficacy as to double the quantity distilled in the same time. This appears to be a great improvement; yet I am not certain whether it can be turned to much advantage. Speculation is fallacious, even experiments in small quantities deceive. Let us hear the ingenious author. . . .6

Here, I am afraid, we shall find a fallacy. The Doctor supposes one hundred and twenty gallons of water ventilated to be distilled, not only in the same time, but with the same fuel as only sixty gallons not ventilated. But surely to heat twice the water in the same time will demand twice the fire. And then there appears to be nothing gained but the room of a still. I pretend not to decide peremptorily: I am speaking of what the Doctor understands better than I. But since ventilation adds no heat to the water, and the water must be hot before it will pass off in a vapour, I think a double quantity of water must require near a double quantity of fuel.7

The next essay in this pamphlet is on the use of ventilators, which seems now to be well understood. The Doctor has given letters from commanders of ships, of which one will be sufficient to keep up the attention of the public, to this may be added the testimony of the Earl of Halifax, that in the transport ships sent to Nova Scotia, the proportion of deaths, in ventilated and unventilated ships, was only one to twelve. . . .8

The Doctor has tried the power of a ventilator upon milk of an ill taste; but its froth made the method impracticable.9 There are however some useful hints for the dairy. . . .1