﻿NO. 7 



SMITHSONIAN EXPLORATIONS, I926 



25 



through which the patiently persistent Nahe has cut its way. But 

 the upper portion of the consolidated mass was full of steam cavities, 

 large and small, like those in a well-raised loaf of bread. Into these 

 the heated waters carried silica in solution and formed agates. In turn, 

 as the rock decayed and the stream cut deeper, these agates being 

 less destructible, accumulated in the soil and ravines, to be collected 

 doubtless at first as mere curiosities. Interest in their banded struc- 

 ture was probably aroused from broken fragments which led to 

 laborious grinding of flat surfaces on sharp-gritted sandstones. Later 

 yet they were ground by holding them against huge revolving grind- 



FiG. 29. — Grinding agates. Oberstein — Idar. 



stones driven by slow-turning undershot water-wheels, the operator 

 lying prone upon a roughly carved wooden form moulded to his chest 

 and abdomen, and with feet braced against a wooden cleat nailed 

 to the floor. This crude system is still followed in many of the 

 smaller shops, but is laborious and unhealthy, the confined position 

 of the lungs and constant dampness from the cold, wet wheel being 

 productive of rheumatism and pulmonary troubles. In all the many 

 " Schleiferei "—shops devoted to gem cutting, and there are some 

 hundreds in the region — the slicing is now done on circular saws of 

 thin metal charged with diamond dust, and the grinding on metal 

 plates revolving horizontally, at which the workmen sit in comfort. 

 Exhaustion of the local supply it may be safely assumed resulted 

 in the reaching out into world-wide sources for new materials, and 



