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.”

“A zimilar remarg was made nod zo very many years ago when id was suggesded that ocean shibs could be buildt of medal,” retorted the professor. “Yed there are thousands of medal shibs in exisdenze do-day; and there can be no doubt as do the facd thad they fload. And zo will an aerial shib. The gread—in facd the only diffiguldy in the madder is thad air is eight hundred dimes lighder than wader; and an air shib of given dimensions musd therefore be ad leasd eight hundred dimes lighder than her ocean sisder do enable her do fload in the atmosphere. The broblem, then, is this: How are you to gonsdrugt a medal shib, of given dimensions, sdrong enough do hold dogether and withsdand the shock of goming do earth, yed of less weighd than her own bulk of air? With the medals hitherdoo ad our disbosal, I admid thad the dask is a diffiguld one; bud I maindain thad id is by no means an imbossibilidy. An ocean shib musd be buildt sdrong enough nod only do susdain the weighd of her gargo—often amounding do upwards of a thousand dons—bud also do withstand the dremendous and incessandly varying sdrain do which she is exbosed when garrying thad gargo through a moundainous sea. This enormous sdrength necessidades the use of a gorresbonding thickness—and therefore weighd—of the medal used in her gonsdruction. Such brovision would of gourse be unnecessary in the gase of an aerial shib; begause no one would dream of garrying an ounze of unnecessary weighd through the air; and there are no moundain seas in the admosphere to sdrain a shib. A vasd saving in weighd would resuld from these zirgumsdances alone; and a further saving—zufficiend, I believe, to aggomblish the desired object—gan, no doubd, be effecded by skilful engineers, one of whose greadesd driumphs id is do design sdrugdures in which the maximum of sdrength is zecured with the minimum of weighd. Id musd nod be forgodden, either, thad an air shib musd, in one imbordand bardigular, be dreated exactly like her ocean sisder. An ocean shib gonsdrugded, say, of sdeel, will sink if filled with wader, begause sdeel is heavier than wader, bulk for bulk; bud bump oud all the wader from her inderior, and if she be proberly gonsdrugded, she will fload on the elemend she is indended do navigade. And the same with an air shib: bump out all or nearly all the air which she gondains, and if she be gonsdrugded in aggordanze with the brincibles I have indigaded, she will fload in the lighder elemend.”

“Upon my word, professor, you have argued your case extremely well,” exclaimed the colonel. “I can see only one difficulty in the way; and that is in the matter of weight.”

“Which diffiguldy I have gombledely gonquered,” triumphantly exclaimed the professor, rising excitedly from his seat with flushed cheeks and flashing eyes. “Do me, Heinrich von Schalckenberg, belongs the honour and glory of having made dwo mosd imbordand disgoveries, disgoveries of ingalgulable value do the worldt, disgoveries which will enable me do soar ad will indo the highesd regions of the embyrean, do skim the surface of the ocean, or do blunge do ids lowesd debths.”

“Bravo, professor; that was positively dramatic!” exclaimed the baronet. “You have mistaken your business, my dear sir; you were undoubtedly born to be an actor. But what are these two most important discoveries of which you so exultantly speak?”

“They are a new medal and a new power,” exclaimed the professor. Then, fumbling in his breast-pocket, he drew forth a wallet from which he extracted a small rectangular plate of—apparently—polished silver. It measured about five inches long by four inches broad, and was about a quarter of an inch thick.

“There, Sir Reginald,” he exclaimed, offering the plate to the baronet, “dell me whad you think of thad.”

“Very pretty indeed,” commented Sir Reginald, as he held out his hand to take it. “What is it? Silver? Phew! No; it can’t be that,” as his fingers closed upon it; “it is far too light for silver. Why, it seems to be absolutely devoid of weight altogether. What is it, professor?”

“Thad, my good sir, is my new medal, which I gall ‘aethereum’ begause of ids wonderful lighdness. See here.”

There was a very handsome cut glass water-jug, full, standing on the table in a capacious salver of hammered brass. The professor took up the jug and emptied it into the salver, almost filling the latter. Then he laid the glittering slab of metal down on the surface of the water, where it floated as buoyantly as though it had been an empty box constructed of the lightest cardboard. The professor raised the salver from the table and agitated the water, to show that the metal actually floated.

“Why, it floats as lightly as a cork!” exclaimed the colonel in the utmost astonishment.

“Korg!” exclaimed the professor disdainfully, “korg is heavy gombared with this. This is the lighdesd solid known. Loog ad this.”

The professor lifted the plate of metal out of the water, and, wiping it dry very carefully with his silk pocket-handkerchief, held it suspended, flat side downwards, between his finger and thumb. Then, when he had poised it as nearly horizontal as he could guess at, he let it go. It wavered about in the air as a thin sheet of paper would have done, and finally sailed aslant and very gently to the ground, amid the astonished exclamations of the beholders, by whom it was immediately examined with the utmost curiosity.

“You have seen for yourselves and gan therefore judge how marvellously lighd this medal is,” continued the professor when the plate had been handed back to him; “bud ids sdrength you musd dake my word for, as I have no means ad hand do illusdrade id. Ids sdrength is as wonderful as ids lighdness, being—zo var as I have had obbordunidy do desd id—exactly one hundred dimes thad of the besd sdeel.”

“If that be the case, professor, then I should say you have solved the problem of aerial navigation,” remarked the colonel. “But you spoke of having also discovered a new power. What is it?”

The professor once more instituted