_Agate Mortar and Pestle._--This mortar is used for the purpose of pulverizing hard substances, and for mixing fluxes. As this mortar will not yield to abrasion, there is no danger of any foreign matter becoming mixed with the substance pulverized in it. It should be cleaned after use with pumice stone. Steel mortars are very useful for the pulverization of hard bodies; but for all those substances which require great care in their analysis, and which can be obtained in very minute quantity, the agate mortar alone should be used. A _hammer_ made of steel is necessary. This should have the edge square. A small _anvil_, polished on the surface, is also required. It is frequently used to test the malleability of metals. A _knife_, for the purpose of ascertaining the hardness of minerals. The student should also be provided with several three-edged files, and likewise with some flat ones. A _microscope_, an instrument with two lenses, or with such a combination of lenses, that they may be used double or single, is frequently necessary for the examination of blowpipe experiments, or the reaction of the fluxes. Common lenses, howsoever cheap they may be, are certainly not recommended. A microscope with achromatic lenses can now be purchased so cheap that there is no longer any necessity of procuring one with the common lens. Besides, there is no reliability whatever to be placed in the revelations of the common lens; while on the contrary, the deceptive appearances which minute objects assume beneath such lenses are more injurious than otherwise. A small cheap set of magnifying glasses are all that is required for the purpose of blowpipe analysis, Fig. 12. [Illustration: Fig. 12.] A small _magnet_ should be kept on hand, for the purpose of testing reduced metals. _Nippers_, for the purpose of breaking off pieces of minerals for analysis, without injuring the entire piece, are indispensable, Fig 13. [Illustration: Fig. 13.] A pair of _scissors_ is required to trim the wick of the and for the trimming of the edge of platinum foil. A small _spatula_ should be kept for the purpose of mixing substances with fluxes. THE REAGENTS. Those substances which possess the property of acting upon other substances, in such a characteristic manner that they can be recognized, either by their color, or by their effervescence, or by the peculiar precipitation produced, are termed _reagents_. The phenomena thus produced is termed _reaction_. We use those reagents, or _tests_, for the purpose of ascertaining the presence or the absence of certain substances, through the peculiar phenomena produced when brought in contact with them.