IS 
Field Museum of Natural History 
once on great sandstone wheels. These wheels are 
often 5 feet in diameter. They contain grooves of dif- 
ferent shapes which fit the various forms of agates. 
Grinding of the agates to desired shapes is performed 
by workmen who lie prone upon a sort of hollow bench 
and, bracing their feet against cleats nailed to the floor, 
force the agates with the pressure of their whole bodies 
against swiftly revolving grindstones (Plate VIII). 
Many of the grindstones are wide enough so that 
two workmen can use the same one at one time, 
one on either side. The agates usually emit a bright, 
phosphorescent light in the process of grinding. The 
stones are kept constantly wet with a stream of wa- 
ter. Both for this reason and for the water power 
needed, the mills in which this work was done were 
formerly all located on the banks of streams. At the 
present time, however, steam and electrical power and 
other modern methods are employed. Vases, bowls 
and such objects are hollowed out by special grind- 
stones, as much advantage as possible being taken of 
the natural contours of the agates. After being ground 
to the desired shapes, the articles are polished, this 
work being done on wooden wheels to which suitable 
polishing powders are applied. This work can be done 
by women and children. Owing to its hardness and 
toughness agate takes a high and durable polish. Be- 
cause of its hardness, toughness and capacity for high 
polish, as well as its pleasing patterns and colors, 
agate has a number of uses in which ornament is com- 
bined with utility. Thus it is made into pen holders, 
handles for dental and surgical instruments, umbrella 
handles, match boxes and toilet cases. Agate bearings 
are of the highest utility for chemical and other bal- 
ances and no chemical laboratory is complete without 
one or more agate mortars. For ornamental purposes 
agate serves for cameos and other stones for breast- 
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