"You may gall it zo iv you like, colonel, I do nod; I call it merely a buoy," returned the professor. "A _ship_ is a zomething gabable of _moving_ in the elemend which zustains it; a balloon is ingabable of any indebendend movement in the air; it drifts aboud at the mercy of every idle wind that blows. Id is like a ship on a breathless sea; withoud any means of brobulsion the ship lies motionless, or drifts at the mercy of the currends. Bud give the ship a means of brobulsion, and navigation ad once begomes bossible. And zo will it be with balloons." "Well, that has already been tried," remarked the colonel; "but the buoyancy of a balloon is too slight to permit of its being fitted with engines and a boiler." "My vriendt," said the professor impressively, "whad would you think of the man who tried to pud the engines and boilers of an Atlantic liner in a leedle boad?" "I should think him an unmitigated ass," retorted the colonel. "Jusd so. Yed thad is whad the aeronauds have been doing; they have been drying to make the leedle boad-balloon garry the brobelling bower of the aerial ship. In other words, they have not made their balloons large enough." "Then you think they have not yet reached the practical limit to the size of a balloon?" asked the colonel. "They have--very nearly--if balloons are do be made only of silk," was the reply. "Bud if _navigable_ balloons are to be gonsdrugded, aeronauds musd durn do other maderials and adobd another form. As I said before, they musd build a _shib_, and she musd be of sufficiend size to float in the air and to garry all her eguipments." "But such an aerial ship would be a veritable _monster_" protested the colonel. "Zo are the Adlandic liners of the presend day," quietly answered the professor. "Phew!" whistled the colonel. The baronet rose from the divan, flung away the stump of his cigar, and settled himself to listen, and perhaps take part in the singular conversation. "And of what would you build your aerial ship, professor?" asked the colonel when he had in some measure recovered from his astonishment. "Of the lighdesd and, ad the zame dime, sdrongesd maderial I gould find," answered the professor. "Once get the aeronaud to realise thad greadly ingreased bulk and a differend form are necessary, and id will nod be long before he will find a suitable building maderial. Iv I were an aeronaud I should dry medal." "Metal!" exclaimed the colonel. "Oh, come, professor; now you are romancing, you know. A ship of metal would never float in the atmosphere."