This defect is similar to what would appear in that system of chemistry which should contain only a physical description of elements of matter, without saying any thing of the various substances which they form in combination. Thus the chemist might describe oxygen by itself. He might say it is a gas, colourless, heavier than common air, a supporter of combustion and animal life, and many other things equally important, interesting, and true; and if such facts were all that is known of this substance, they should be received and appreciated according to their value. But how much is added to our knowledge, when we are informed that oxygen enters into combination with almost every other element of matter? That in one combination it forms the deadly poison; in another, the refreshing cordial. That united with nitrogen in one proportion, it constitutes the air we breathe; in another, it forms the nitrous oxyde, a substance producing the most remarkable effects of exhilaration; in a third proportion, the nitrous oxyde, which, coming in contact with our lungs, produces instant death; and in a fourth, one of the most powerful agents in nature. That with hydrogen it forms the valuable substance called water; and in other various combinations, acids so valuable in the arts and all the economy of civilised life. Much likewise might be said, which would be interesting and true, of acids—of their general properties—their sour taste—their effects on vegetable blues, &c.; but how imperfect would be the description which should fail to give us not only the elements of which each is composed, but the nature of those substances which they form in compositions? We have room only for a single example to illustrate the truth of our position. We select the mental power termed by Dr. Brown “_anger_;” in phrenology, “Combativeness.” In his description of this feeling, Dr. Brown is truly eloquent. His organ of Combativeness must have been large, or he could not have described the feeling with such vividness and accuracy.