Cyclopedia of practical information Author:Charles Morris This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1900 Excerpt: ...the selection of the materials, and the proportion of lime used is somewhat less than in the other two kinds. 2. Bohemian glass consists o... more »f silicates of potassium and calcium. This glass is very hard and difficult to melt, and is much used for chemical apparatus, or whenever a glass is required which can withstand heat. 3. Flintglass, or crystal, contains silicates of potassium and lead. It is employed for table glass, globes, ornaments, etc. Glass for optical purposes is made both of flint and crown glass. 4. Bottle glass is an impure mixture of various silicates, such as sodium, calcium, iron, and aluminium. In this variety the color and quality of the glass are not of the same importance as in the other three kinds. In glass manufacture the materials are melted together in a highly heated crucible. A portion of the melted mixture is then taken up by the glassblower on the end of a long tube, and blown by him intoa hollow pearshaped bulb. It is then given the desired shape by various processes of handling. Many articles of glass are formed in moulds, and other methods of manufacture arc employed. The grinding and cutting of glass are subsequent processes for the purpose of ornamentation. Glass-sponge. A sponge which forms a framework of spicules of silica, which, when the fleshy parts are washed away, looks like the finest spun glass. One species is thehandsome Venus flowerbasket, another is the Japanese glass rope sponge. Globe. Fr., from h. globus, ball. A round body imitating the earth and made of some light material. At two opposite points are fixed two pins, round which it turns; these are called the poles. The two pins produced through the centre represent the axis of the globe. The pins turn in two holes made in a brass circle surrounding the globe...« less