by other means of travel, and visiting places which travellers have never penetrated, would be of immense use in the science of geography: and when under the line, if the heat near the earth should be inconvenient, the aeronauts would, of course, easily rise to elevations where the temperature is equal and agreeable. When their observations, their needs, or their pleasures demanded it, they could descend to within a short distance of the earth, say ninety feet, and fix themselves in their position by means of an anchor. It might, perhaps, be possible, by taking the advantage of favourable winds, to make the tour of the world. "Experience will perhaps demonstrate that aerial navigation presents less inconvenience and less dangers than the navigation of the seas."
The immensity of the seas seemed to be the only source of insurmountable difficulties; "but," says Robertson, "over what a vast space might not one travel in six months with a balloon fully furnished with the necessaries of life, and all the appliances necessary for safety? Besides, if, through the natural imperfection attaching to all the works of man, or either through accident or age, the balloon, borne above the sea, became incapable of sustaining the travellers, it is provided with a boat, which can withstand the waters and guarantee the return of the voyagers."
Such were the ideas promulgated regarding the "Minerva." The following is the serious description given of the machine. The numbers correspond with those on the illustration.
"The cock (3) is the symbol of watchfulness; it is also the highest point of the balloon. An observer, getting up through the interior to the point at which the watchful fowl is placed, will be able to command the best view to be had in the 'Minerva.' The wings at the side (1 and 2) are to be regarded as ornamental. The balloon will be 150 feet in
