Apeil 7, 1911] 



SCIENCE 



519 



account for the origin of glass making, it 

 is altogether likely that glazes and enamels 

 were the immediate forerunners of glass. 

 Glass manufacture had its origin in Egypt, 

 not far from 2500 B.C. "Wlio shall say that 

 the natural mineral resources of the coun- 

 try (among them limestone, sand and 

 alkalis) were not responsible for its origin 

 there ? It spread to the countries east and 

 north of Egypt to Greece and Rome, to 

 Spain, France and more recently to Sax- 

 ony, Bohemia and Austria — finally over 

 the civilized world. At the present time 

 the data for a history of glass manufacture 

 are probably as complete and available as 

 that for any other of the chemical indus- 

 tries — and possibly more so. The ancient 

 glasses were usually not perfectly trans- 

 parent but were translucent, in some cases 

 nearly opaque. Transparent glass and 

 particularly transparent glass in large 

 sheets, is a modern production. Many of 

 the ancient glasses and those of early mod- 

 em times possessed great beauty, consid- 

 ered from the standpoint of the fine arts, 

 although their utility as light transmitters 

 is low. In Greece and Rome glass was 

 used for plates and saucers and other table 

 ware, for pitchers and ornamental objects, 

 as tile in pavements and walls, but scarcely 

 at all in windows. With the advent of 

 transparent glass the production of the 

 translucent varieties did not expand, until 

 finally the art languished in many coun- 

 tries and has but recently been revived for 

 many decorative purposes. It should be 

 noted that the art was never really lost, but 

 the interest in and demand for translucent, 

 tinted and roiigh-surfaced glass was low. 



The dyeing industry is another which 

 dates from the remotest antiquity and 

 which was developed without the aid of 

 scientific chemistry, on an empirical 

 groundwork. However, ancient colors, 

 largely derived from vegetable sources. 



were reproducible. The use of mordants 

 was practised by many ancient peoples, 

 particularly by the ancient Egyptians, who 

 used them not only for fixing colors, but for 

 producing different shades from the same 

 dye bath. With increasing commerce be- 

 tween nations, new sources of dyes became 

 available and the vegetable-dyeing practise 

 had reached a high degree of perfection 

 when the coal-tar dyes were brought forth 

 in the chemical laboratory to the wonder- 

 ment of mankind and the revolutionizing 

 of the industry. It has never been 

 claimed, I believe, that the art of dyeing 

 with vegetable colors has been lost or not 

 practised. But there is a strong tendency 

 at the present time to disparage the aniline 

 colors. It is very commonly said and ac- 

 cepted as true that vegetable dyes are su- 

 perior to coal-tar dyes. That vegetable 

 dyes are fast and coal-tar dyes are not. 

 Persia has recently prohibited the exporta- 

 tion of rugs and fabrics dyed with any- 

 thing but vegetable dyes, ostensibly to 

 maintain her reputation in the rug in- 

 dustry. Who shall come forward and 

 refute these charges, which are of course 

 all but groundless? There are good and 

 bad dyes, both coal tar and vegetable, and 

 the best dyes must be skilfully used to 

 produce good results. Let us hope that 

 the coal-tar dyes will be increasingly ap- 

 preciated, and that the time will not come 

 when people will lament the lost art of 

 vegetable dyeing! 



But what about the cement and plaster 

 of the ancients which outlasted the ages 

 and even the stones which it held together? 

 In the first place any cement or plaster 

 which was not remarkably durable could 

 not possibly have been preserved to this 

 day. The ancients in various countries 

 and at various times have been well ac- 

 quainted with lime, burned clay-limestone 

 (hydraulic lime), hydraulic cement, vari- 



