THE USE OF WATERJETS IN CUTTING A MULTIPLE PHASE MATERIAL
The University of Missouri-Rolla is carving a new sculpture. This involves shaping 3 rocks, collectively weighing 100 tons, and cutting figures of a man and a woman from two blocks. The three blocks will then be erected to form a Millennium Arch and the Figures will be polished as a second set. A relatively inexpensive X-Y table and cutting head unit were developed. The cutting waterjet was without abrasive at under 100 MPa. One problem in cutting large blocks (5 m x 2 m by 0.75 m) is that the structure changes. A variety of approaches were taken to solve this problem. The process steps required to cut the rock to shape, and then to carve the rock are described in the paper.
THE EFFECT OF ROCK ANISOTROPY ON THE EXCAVATION RATE IN BARRE GRANITE
The variation in the volume of rock removed when a water jet traverses over a sample of Barre Granite is shown to vary with the angle at which the sample is cut relative to the orientation of the main deposit. For example where the jet impacts perpendicular to a microfissure plane a channel up to 10 times the volume is cut as when the jet is traversed along the microfissure plane. A correlation is shown to exist between the dimensions of the rock volume removed and the angle of impact between the water jet and the two microfissure planes of the Barre Granite.
Early Cretaceous Feathers from Victoria
Unusually well preserved fossil feathers from Lower Cretaceous (VaIanginian-Aptian) claystones at Koonwarra, Victoria, are the oldest (c. 110-125 million years) bird remains yet found in the southern hemisphere, They are among the oldest bird remains known in the world, being antedated only by the toothed Archaeopteryx from the late Jurassic of Bavaria, and being more or less the same age as Gallornis from the Lower Cretaceous of France. The Victorian fossil feathers are evidence for essentially worldwide distribution of birds soon after the beginning of the Cretaceous, if not before. The feathers could conceivably have come from toothed birds.