At some date during the period we are now discussing we must place the discovery of glass. Glass beads of a blue or green colour are, in fact, found in the tombs of the bronze epoch. What was their origin? Chemistry and metallurgy combine to inform us that as soon as bronze foundries existed glass must have been discovered. What, in fact, does glass consist of? A silicate with a basis of soda and potash, combined with some particles of the silicates of iron and copper, which coloured it blue and green. As the scoria from bronze foundries is partly composed of these silicates it is indubitable that a kind of glass was formed in the earliest metal-works where this alloy was made. It constituted the slag or dross of the metal works. Thus, the classic tradition which attributes the invention of glass to certain Phoenician merchants, who produced a mass of glass by heating on the sand the _natron_, that is _soda_, brought from Egypt, ascribe too recent a date to the discovery of this substance. It should properly be carried back to the bronze epoch. The working of amber was carried out to a very great extent by these peoples. Ornaments and objects of this material have been discovered in great abundance in the lacustrine settlements of Switzerland. On the whole, if we compare the industrial skill of the bronze age with that of the preceding age, we shall find that the later is vastly superior to the earlier. The art of weaving seems to have been invented during the stone age. We have positive and indisputable proofs that the people who lived during this epoch were acquainted with the art of manufacturing cloth.[36] All the objects which we have thus far considered do not, in fact, surpass those which might be expected from any intelligent savage; but the art of preparing and manufacturing textile fabrics marks out one of the earliest acquisitions of man's civilisation. In the Museum of Saint-Germain we may both see and handle some specimens of woven cloth which were met with in some of the lacustrine settlements in Switzerland, and specially at Robenhausen and Wangen. This cloth, which is represented in fig. 203, taken from a specimen in the Museum of Saint-Germain, is formed of twists of interwoven flax; of rough workmanship, it is true, but none the less remarkable, considering the epoch in which it was manufactured. It is owing to the fact of their having been charred and buried in the peat that these remains of pre-historic fabrics have been kept in good preservation up to the present time. [Illustration: Fig. 203.--Cloth of the Bronze Age, found in the Lacustrine Settlements of Switzerland.] Balls of thread and twine have also been found; likewise ends of cord, and ropes made of bark, nets with large and moderately-sized meshes, which we have previously represented, and lastly some fragments of a basket of straw or osier.