Discussion of a paper by Murthy and Patterson. The isotopic composition of Pb of the Boulder batholith is based on the composition of Pb from quartz of one sample (S-1) and may not be representative of the whole quartz monzonite mass. Rejection of feldspar Pb data by Murthy and Patterson because of supposed Pb contamination may be unwarranted. Slight cloudiness of the K feldspar is a primary or at most a deuteric feature. If the batholithic model is not restricted to 2 dimensions but includes depth as well, the hypothesis of Murthy and Patterson need not necessarily depart from the classic hydrothermal epigenetic theory.