What are nichills?

Reading the Black Book, a compendium of the iniquities of the governance of England in 1830 (quite a thick tome, I am sorry to have to report), I came across this exposition of the waste in the Exchequer:-

The exchequer is divided into seven different departments; the tellers, the pells, the king's remembrancers, the lord treasurer's, the auditor's office, the tally court, and the pipe office. The pipe office alone has seven subsidiary absurdities; among these are the clerk of the nichills, the clerk of the estreats, and the cursitor baron...

I have managed to run down most of this but cannot find a definition for nichills; there is one here but it is cut off, and requires a subscription for the rest. So, does anyone know what nichills are?

Solution 1:

From the reference indicated by StoneyB above -- The New English Dictionary on Historical Principles:

Nichil, sb, obs.

1. Nothing, naught.

2. Law. The return made by the sheriff to the exchequer in cases where the party named in the writ had no goods upon which a levy could be made.

   b. Clerk of the Nichils, a clerk of the exchequer who made note of the nichils returned by the sheriff.

(Extraneous details omitted.)

There is also a verb defined, equally indecipherable.