The importance of long reaction times in the coalification process has been demonstrated in the laboratory. Samples of cellulose and pine sawdust in evacuated, sealed glass vials have been heated at 200 deg. C for 2 years. Black coal-like chars were produced; conventional heating at 200 deg. C for hours produces very little chemical change. The chars were characterized by infrared and electron spin resonance spectra and by ultimate analysis. The infrared spectra of the pine sawdust char and of a subbituminous coal are nearly identical, except for differing carbonyl absorption. The spectrum of the cellulose char is also similar to that of the subbituminous coal. The electron spin resonance (esr) results show that g values, line widths, and spin concentrations are very similar for the two chars, and resemble closely the corresponding values for subbituminous coal. 200 deg. C is considered a reasonable coalification temperature; a feasible depth of burial can provide such temperatures. The experimental coalification obtained in only 2 years supports the hypothesis that geologic time could produce all ranks of coaIs, from lignite to anthracite, at temperatures below 200 deg. C.