Is sugar sweet? That sugar has certain chemical constituents which go to make up a saccharine compound we know. But what evidence have we of its sweetness, except that the nerves of taste are peculiarly affected when brought in contact with it. Its sweetness is not measurable in the chemist's scales. It can be analyzed, and its constituent elements accurately defined. But sweetness is not one of those elements. The test of that is the tongue. Pure sugar of milk has scarce any sweetness at all; nevertheless, it is pure sugar. The influence which it has on the nerves of taste is only different from that of cane-sugar. Destroy the nice nervous connection between the tongue and the brain, and sweetness disappears. A severe cold will accomplish this, and while the touch of the sugar is felt, the delicate sympathy which is awakened by the sugar and is felt in the brain as sweetness is destroyed. The sweetness, like the color, is a nervous sensation. We can conceive of a development of the nerves of taste which might receive a host of new impressions from contact with objects now tasteless. The saccharine compound does exist as a chemical quantity, and has a special effect on the nerves of taste, exciting them peculiarly, the result of the excitement being the idea of sweetness. Is the rose fragrant? The sense of smell is indeed only a continuation of that of taste. In smelling, the nerves are touched by only infinitesimally small particles of the substances reaching them, and are only able to receive an impression from this excessive distribution. This is also true of taste, to a certain degree, as it is impossible to fully perceive a flavor until the substance is tolerably comminuted, as we smack our lips to obtain it. Indeed, it may be questioned whether the whole of taste may not lie in the capabilities of different substances for great subdivision of particles. If quartz could be made to dissolve into excessively minute particles as readily as sugar, it might have its own special flavor. Some odors are offensive in dense quantities which are highly agreeable when wafted to us in delicate atoms,--musk, for instance. The rose secretes a volatile oil, the wonderfully small atoms of which, on touching the nerves of smell, communicate a peculiar sensation. This odor, like the sweetness, exists only in the nerves affected; and a trifling disaffection of the nerves suffices to destroy it entirely. The chemist can also analyze the oil, but he does not enumerate in its elements odor. In fact, we have no words to express the sensation of smell. We say sweet, sour, bitter; but have no terms to express the differing sensations produced on us by the rose, lily, violet, and pink. Their oily atoms awaken different sensations in the delicate nerves they touch. The sensation awakened may be due to chemical action induced by them in the system. But whether chemical or physical, the result of their touch is a motion of matter,