Even a crude grist mill was an important “machine” in 1840s frontier California, because without it flour and bran and cornmeal had to be imported at considerable cost. Most were simple, out-in-the-open constructs. The grinding stones consisted of two individual stones: the bottom, or bed stone, which remained in place and the runner stone on top, which turned, via a lashed-on wooden lever powered by men or mules. The pieces were thick, heavy, circular chunks of quarried stone joined by an axle fixed into the bed stone and through a hole in the runner stone. Axles were slightly off-center so that the top-stone turned in an ellipsis over the bed stone. Troughs and ridges chiseled in both layers pulverized wheat berry into flour as the wheat berry was poured between the stones through a large funnel. If the stones were turned too fast, friction heat burned the flour, and burnt flour made burnt-tasting bread. Because of this it was important for the miller to frequently bend over the grindstone to smell for burning flour. The saying “keeping your nose to the grindstone” comes from this practice.