the wind only, as Mr Kalm seems to think.  Neither did they confine themselves to a strait-lined course, but frequently were seen to describe a curve.  When they met the top of a wave as they skimmed along the surface of the ocean, they passed through, and continued their flight beyond it.  From this time, till we left the torrid zone, we were almost daily amused with the view of immense shoals of these fishes, and now and then caught one upon our decks, when it had unfortunately taken its flight too far, and was spent by its too great elevation above the surface of the sea.”—­G.F.

[3] “About this time, the captain ordered the ship to be fumigated with gunpowder and vinegar, having taken notice that all our books and utensils became covered with mould, and all our iron and steel, though ever so little exposed, began to rust.  Nothing is more probable than that the vapours, which now filled the air, contained some saline particles, since moisture alone does not appear to produce such an effect.”—­G.F.

There can be no doubt that the atmospherical air is capable of sustaining marine salt in a state of solution, and of bearing it off to great distances on land, where it serves important purposes in animal and vegetable economy.  The reader will be pleased with some remarks on the subject in Robison’s Account of Black’s Lectures.  The air in the vessel, then, it will be readily imagined will contain it, and hence, as it is known that it is gradually decomposed by iron, the rust that was observed.  The process of corroding the iron, &c. as it is commonly called, would be much accelerated by moisture, as the muriatic acid acts most powerfully on bodies capable of decomposing water; and it is no less certain, that the heat of a tropical climate would aid the operation.  But it is difficult to explain how any benefit could be derived from the fumigation said to be practised by Cook on this occasion, otherwise than by producing dry warm air.  Indeed, many persons will imagine that the circumstances required nothing more than free ventilation, and the occasional use of fires to destroy moisture.  Mr Forster takes particular notice of what is mentioned in the text about the fermentation of the inspissated juice of malt, or, as he calls it, essence of beer; and he says, that, by the advice of his father, a vessel strongly fumigated with sulphur was filled with it, and prevented the fermentation for a few days.  He does not explain on what principle, and perhaps was not acquainted with it.  The fact is, that sulphuric acid, which is produced by the burning of sulphur, has the power of checking, or altogether destroying, the fermentation of substances.  In the present case, it seems, enough of it had not been produced to answer the purpose effectually.  Some other acids have the same power.  Hence the desideratum mentioned in the text is easily supplied.  The juice, it may be thought, will be changed by the addition of a strong acid, and