GLASS-MAKING. 1 5 7 



GLASS-MAKING. 



By C. HANFORD HENDERSON, 



PROFESSOR OF PHYSICS AND CHEMISTRY IN THE PHILADELPHIA MANUAL TRAINING SCHOOL. 



IV. — IN THE ATELIER OF A GLASS-WORKER. 



THERE are few objects of manufacture which better than 

 glass illustrate the immense preponderance in value of hu- 

 man labor over crude material. It is a substance which might 

 serve economists as a parallel to their favorite illustration of the 

 comparative values of a steel watch-spring and the bit of iron- 

 bearing earth from which it is wrought. 



In the case of glass, the crude materials are so plentifully dis- 

 tributed in nature as to be almost valueless. The basis of the 

 compound, sand, is so very abundant that it has furnished the 

 symbol, in more than one parable, for quantity without limit. 

 Like the unnumbered sands of the sea was a vast promise to 

 the children of men. Somewhat less abundant than the sand are 

 the other chemicals which it is necessary to mix with it in order 

 to produce that double silicate which goes under the general name 

 of glass. They are, however, far from being either scarce or ex- 

 pensive. The alkaline ingredient, the carbonate of soda, is made 

 from common salt, a mineral whose wide distribution in nature is 

 at once apparent when one recalls the fact that the sea, thirty or 

 forty times in bulk the total elevated mass of the earth, is one- 

 vast storehouse of the substance ; that salt springs or brines 

 abound at our very doors — in New York State, in Michigan, and 

 in Virginia ; and that vast deposits of the solid rock-salt are to be 

 found in Louisiana and Prussia. The third ingredient, the lime, 

 is simply calcined limestone, a rock which forms whole ranges of 

 hills, and is found in every corner of the globe. For the produc- 

 tion of the fine flint glass, or crystal, which forms the special sub- 

 ject of the glass- worker's skill, it is also necessary to add a fourth 

 ingredient, red lead or minium. As this is the oxide of an easily 



ure, vol. i, p. 24. As to astronomical knowledge evidenced by the Great Pyramid, see 

 Tylor, as above, p. 21. For delineations of vases, etc., showing Grecian proportion and 

 beauty of form under the fourth and fifth dynasties, see Prisse, vol. ii, Art Industriel. 

 As to the philological question, and the development of language in Egypt, with the hiero- 

 glyphic system of writing, see Rawlinson's Egypt, London, 1881, chap, xiii; also Le Nor- 

 mant; also Max Diincker, Geschichte des Alterthums, Abbot's translation, 1877. As to 

 the medical papyrus of Berlin, see Brugsch, vol. i, p. 58, but especially the Papyrus Ebers. 

 As to the corruption of later copies of Manetho and fidelity of originals as attested by the 

 monuments, see Brugsch, chap. iv. As to the accuracy of the present Egyptian chronology 

 as regards long periods, see ibid., vol. i, chap, xxxii. As to the pottery found deep in the 

 Nile and the value of Horner's discovery, see Peschel, Races of Man, New York, 1876, pp. 

 42-44. For succinct statement, see also Laing, Problems of the Future, p. 94. 

 vol. XXXVII. — 12 



