Direct observations on the process of dolomitization are all but lacking. Its limiting conditions have not been found by experiments. Field and petrographic facts, therefore, are at present the best bases from which inferences as to its nature, may be attempted.
Thus far most studies on. the origin of dolomite have been based on (1) published field and petrographic facts of a general nature which were not collected with the specific aim of throwing light on the dolomite question, and (2) generalizations which grew out of the general field and petrographic facts just alluded to. To this type of inquiry into the origin of dolomite the writer2 contributed in 1911. H e is now convinced that progress on the dolomite problem will be made chiefly by direct studies of dolomites themselves. This paper presents the principal results of his first attempt by the direct method.
A perplexing difficulty involved in . . .