That, in effect, constituted the essential difference between these two firm friends. Gerald was fond of indulging in speculations concerning all kinds of scientific research. The mysteries of the unknown, and the as yet ’undiscovered;’ the limitless possibilities lying in the worlds surrounding our globe—speculations concerning such themes as these had for him an irresistible fascination. Jack, on the other hand, kept his thoughts and interest fixed upon the practical side of everything about him. He was a skilful mechanic and a trained mathematician, and had developed clever engineering abilities; he might possibly some day become an inventor. But speculative, dreamy fancies had little attraction for him. ’Jack,’ said Gerald impressively, ’I can’t come in just now—I really cannot! I can’t exactly say why, but to-night I seem to be unusually restless. I could not sit down indoors, nor could I rest if I went to bed. I don’t know what it is; but I have a feeling’—— ’It’s the electricity in the air. I suppose there must be more lying about loose to-night than suits your constitution,’ remarked Jack prosaically. ’I said a minute or two since that you were as dreamy at times as any girl. I begin now to think you are developing "nerves" as well. However, do as you please! Stop here and enjoy yourself with your "nervy," dreamy fancies if you choose. For my part, I ’m going in to supper, and’—— ’What are you lads talking about?’ This question, which came from some one behind them, caused the two friends to start suddenly, and then glance at one another with wondering looks. It was not that they had not recognised the voice. They knew it at once to be that of Mr Armeath, their guardian; the wonder was that he should have come out to them. Usually he spent the whole night shut up in his own rooms, immersed in his studies, or gazing through his telescope at the heavens above; for, amongst other things, he was an enthusiastic astronomer. ’Faith!’ exclaimed Jack, in an aside to Gerald, ’I begin to think you ’re right after all. There must be something unusual in the air to account for this new move!’ The new-comer was a tall, fine-looking old man, with an ascetic face and a kindly voice and manner. His hair and beard were white, but his deep-set eyes glowed with the liveliness and fire of a vigorous young man. With the self-absorbed, thoughtful air that so often marks the devoted scientist or profound student, Armeath, without waiting for any reply to the question he had asked, stepped past the two youngsters and walked almost to the edge of the bluff. There he gazed first at the sandy shore fifty feet or more below, then out over the glistening sea to the distant horizon, and finally at the deep-blue, star-spangled sky overhead.