Although hesitant to discuss the subject of isostasy, the writer cannot agree with Dr. Lawson's article on Isostasy of the Uinta Mountains. Dr. Lawson gives far greater credit to isostasy and assigns much less to compression in the formation and present relief of these mountains than is warranted by the geologic evidence presented by them. The outstanding structural features of the Uinta Mountains, the overturned anticline, and the low angle thrust faults, should prove that compression, not isostasy, was the dominant factor in the diastrophism. The principle of isostasy is a factor which must be considered in mountain building, but only in a minor not a major r61le in the formation of mountains of this type. Two statements of Dr. Chamberlin's fit this case very aptly:2 To the geologist the recognized geologic facts, which he can understand and appreciate, are vastly more convincing than mathematical interpretations based upon assumptions, some of which he does not understand, and others of which seem to him clearly at variance with the actual earth conditions. Though the mathematical mill grinds with precision, the mill has been fed so commonly. with defective assumptions and untruths in past application to geological problems that the grist has often proved more deleterious than beneficial. Past experience justifies the geologist in viewing with caution and skepticism mathematical deductions which seem inconsistent with field observations logically interpreted. Isostasy, though a working principle, can be overworked.