It will be profitable, therefore, for us to briefly describe the blowpipe and the most common of its accessories, stating results obtained in dealing with substances frequently met with in brick-earths. With but little practice anyone can use the instrument, though, as with most other methods of scientific investigation, it requires expert knowledge to yield really excellent results. The simple minerals and compounds to which we shall direct attention may be detected with the greatest ease. The essential constituents of a blowpipe outfit are as follow:-- 1. Blowpipe. 2. Lamp. 3. Platinum-pointed forceps. 4. Platinum wire. 5. Charcoal. 6. Glass tubes. 7. Chemical reagents. 8. Miscellaneous articles. [Illustration: Fig. 5.--Blowpipes.] _1. The Blowpipe._--Common forms of blowpipe are shown in fig. 5. A may be described as follows. It consists of three separate parts: a tube _a b_ having a mouthpiece; an air chamber _c_ to retain moisture caused by the breath of the person blowing; and a side tube _d_ ending in a platinum-tipped jet. Another form of blowpipe, which, however, does not differ essentially from that just alluded to, is shown in fig. 5, B. It is not absolutely necessary to have the jet made of or tipped with platinum, though certain examinations with the instrument are facilitated by the use of such a tip. An essential point is, that the hole in the jet should be of proper size, usually about 0.4 mm. The trumpet-shaped mouthpiece shown in the diagram may be dispensed with. [Illustration: Fig. 6.--Blowpipe Lamp, &c.]