The fifth division will constitute the intellectual part, so to speak, of the exhibition. It will be devoted to lectures, and to scientific meetings for the discussion of questions relating to teaching, to the arts, to the sciences, to hygiene, to international jurisprudence, and to political economy. Questions of colonial economy will naturally occupy the first rank. As will be seen, the programme of this grand scheme organized by the Netherlands government is a broad one; and, owing the experience acquired in recent universal exhibitions, especially that of Paris in 1878, very happy results may be expected from it. At present, we give an illustration showing the general plan of the exhibition. In future, in measure as the work proceeds, we shall be able to give further details.--_Le Genie Civil_. * * * * * NEW METHOD OF DETECTING DYES ON YARNS AND TISSUES. By JULES JOFFRE. The reagents employed are a solution of caustic potassa in ten parts of water; hydrochloric acid diluted with an equal bulk of water, or occasionally concentrated; nitric acid, ammonia, ferric sulphate, and a concentrated solution of tin crystals. The most convenient method of operating is to steep small portions of the cloth under examination in a little of the reagent placed at the bottom of a porcelain capsule. The bits are then laid on the edge of the capsule, when the changes of color which they have undergone may be conveniently observed. It is useful to submit to the same reagents simultaneously portions of cloth dyed in a known manner with the wares which are suspected of having been used in dyeing the goods under examination. RED COLORS. By the action of caustic potassa, the reds are divided into four groups: 1, those which turn to a violet or blue; 2, those which turn brown; 3, those which are changed to a light yellow or gray; 4, those which undergo little or no change. The first group comprises madder, cochineal, orchil, alkanet, and murexide. Madder reds are turned to an orange by hydrochloric acid, while the three next are not notably affected. Cochineal is turned by the potassa to a violet-red, orchil to a violet-blue, and alkanet to a decided blue. Lac-dye presents the same reactions as cochineal, but has less brightness. Ammoniacal cochineal and carmine may likewise be distinguished by the tone of the reds obtained. A characteristic of madder reds is that, after having been turned yellow by hydrochloric acid, they are rendered violet on treatment with milk of lime. A boiling soap-lye restores the original red, though somewhat paler. Artificial alizarine gives the same reaction. Turkey-reds, however, are quite unaffected by acid. Garancine and garanceux reds, if treated first with hydrochloric acid and then with milk of lime, turn to a dull blue.