_Brittle Metals._ ARSENIC, BISMUTH, ANTIMONY, MANGANESE, TELLURIUM, COBALT, TUNGSTEN, MOLYBDENUM, TITANIUM, CHROME, URANIUM, COLUMBIUM _or_ TANTALIUM, IRIDIUM, OSMIUM, RHODIUM.* [Footnote *: These last four or five metallic bodies are placed under this class for the sake of arrangement, though some of their properties have not been yet fully investigated.] CAROLINE. Oh, what a formidable list! You will have much to do to explain it, Mrs. B.; for I assure you it is perfectly unintelligible to me, and I think rather perplexes than assists me. MRS. B. Do not let that alarm you, my dear; I hope that hereafter this classification will appear quite clear, and, so far from perplexing you, will assist you in arranging your ideas. It would be in vain to attempt forming a division that would appear perfectly clear to a beginner: for you may easily conceive that a chemical division being necessarily founded on properties with which you are almost wholly unacquainted, it is impossible that you should at once be able to understand its meaning or appreciate its utility. But, before we proceed further, it will be necessary to give you some idea of chemical attraction, a power on which the whole science depends. _Chemical Attraction_, or the _Attraction of Composition_, consists in the peculiar tendency which bodies of a different nature have to unite with each other. It is by this force that all the compositions, and decompositions, are effected. EMILY. What is the difference between chemical attraction, and the attraction of cohesion, or of aggregation, which you often mentioned to us, in former conversations? MRS. B. The attraction of cohesion exists only between particles of the _same_ nature, whether simple or compound; thus it unites the particles of a piece of metal which is a simple substance, and likewise the particles of a loaf of bread which is a compound. The attraction of composition, on the contrary, unites and maintains, in a state of combination, particles of a _dissimilar_ nature; it is this power that forms each of the compound particles of which bread consists; and it is by the attraction of cohesion that all these particles are connected into a single mass. EMILY. The attraction of cohesion, then, is the power which unites the integrant particles of a body: the attraction of composition that which combines the constituent particles. Is it not so? MRS. B.