Before I tell you of this second day of the Jubilee, I have a few incidents of interest wherewith to prelude it. And first, the organ itself is a noteworthy feature here, for it is the back-bone of the music, which holds the ribs and small bones of the Jubilee, keeps them in place, and prevents fracture. The organ was manufactured by the Messrs. Hook, expressly for the occasion, in the short space of four weeks, and was built with the design in view of combining strength and volume of tone with the least possible space in occupancy. The instrument has a very novel appearance, for the reason that it stands without a case. Above a very slight casing of chestnut and walnut, all the pipes of the "flute a Pavilion" are displayed--a stop which answers to the "Open Diapason." Behind these and others are the pipes of the "Bombarde," a sixteen-feet reed stop, and, still behind these, the vast wooden pipes of the "Grand Sub Bass," which form a double wall across the rear of the organ. On each side are the pipes of the "Pedale Posanne." The grouping of the pipes is very symmetrical, and presents quite as imposing, if not so beautiful an appearance as an elaborate case. The width of the organ across the front is twenty-two feet, and the height thirty feet. The wind-pressure used is at least four times that of ordinary organs, requiring four thousand pounds weight upon the bellows. Notwithstanding its great power, the tone is by no means harsh, but very agreeably rich and pleasant, and combines great intensity and solidity with the most brilliant seriousness conceivable. Its marvelous power and volume were specially manifested yesterday, when the orchestra began to break in the "Star-Spangled Banner." Mr. Wilcox, for a moment, seemed to be gathering up the resources of the organ in his hands, and then let it out in a manner which resembled the rushing of a storm more than anything else; but it had the effect to bring order out of chaos, and when once more he gathered back and restrained its powers, the instruments were playing like a charm.