Damage to a specimen, or to the air scribe itself, can occur in several ways. Almost always it is due to operator error. The air scribe is very powerful and quite capable of quickly boring into mineralized bone or shell--with dire consequences. The reciprocating, or in-and-out, movement of the tool can actually pull the bit through the specimen in a series of chopsawblades millisecond-long bites that can leave the operator in a panic. The secret is to completely familiarize yourself with surface texture, color, and physical properties of both the fossil and the matrix--these are unique and vary greatly between specimens. Let the machine do the work. Knowledge of texture and color lets you know when to lighten up and pull away, and, for the most part, the movement of the chisel tip without any help except guidance from the operator is sufficient to reduce matrix to a fine debris. This is perhaps the most difficult technique to learn because it is human nature to think that force from our own muscles will make the job faster. Quite the contrary, the application of too much pressure chopsawblades only ensures that your lab will be filled with an incessant whining, your air scribe life span will be considerably reduced, and you may snap off fairly expensive chisel bits. In addition, because air scribes are so powerful, the bit should never be used as a lever. It is the reciprocating movement of the tip of the bit that effectively breaks apart the rock matrix. Wedging the bit into the rock, twisting, or levering off larger chunks not only breaks chisel bits, but also rapidly transforms your air scribe into a useless paperweight. With proper care, common sense, and regular lubrication, a pneumatic air scribe will last for years and will enable you to prepare fossils from nearly any matrix. Lab technicians are also finding that air scribes enable them to develop fossils in a way never before available to them, bringing out details of specimens impossible with older, more traditional technologies.

In the summer of 1999, we had used the bottom two layers of 3T to provide autonomous control for a single subsystem--a second-generation biological water processor--during a 450-day, 24-hour-a-day, 7-day-a week test. Then in January 2000, the Advanced Water Research Group received ALS funding for the year-long IWRS test, involving four advanced water-recovery subsystems (Bonasso 2001) (see Advanced Water Recovery System sidebar).BuildupUsing 3T allowed us to develop the control for the IWRS in a modular fashion in two ways. First, moving from bottom to top (figure 4), each layer has its own data structures, timing constraints, and development tools that allow for parallel development of the software. Thus, we were able to develop skills sets based on the evolving hardware specifications and simultaneously develop the sequencer procedures. Early on, as the water research team developed the design for each subsystem, one part of the 3T team wrote the sequencer procedures for each subsystem in the RAPS language (which, in turn, is written in Lisp) (1) using virtual skills, that is, Lisp skills connected to a Lisp simulation of the expected hardware. A virtual simulation of, say, the reverse-osmosis subsystem could then be shown on a laptop to the WRS engineers and the control design refined in an iterative process even before the actual hardware was available. The primary result of this process was a set of skill specifications for each subsystem (figure 5).

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