Going westward the proportion of neptunite to benitoite in- creases until the latter practically disappears before the stringers die out in that direction.

It would be interesting to determine whether the serpentine intrusion has had any direct effect on the production of the phenomena described. General considerations seem to the writer to indicate that it had.

The most suggestive characters of the deposit in this connec- tion are perhaps the similarity in nature of the general meta- morphism of the enclosing rock-lens to the more active alteration in immediate proximity to the vein on the one hand; and on the other hand the correspondence of the albitic alteration, the albite stringers of the country, the albite of the thin zone, and the natrolite in the benitoite veins which are all related chemically and by field relations. In other words, the general rock changes which seem to demand a general elevated temperature for their consummation, appear genetically related forerunners of the local action along the veins. Such a general elevation of temperature was undoubtedly supplied by the peridotite intrusion, and that occasion is most naturally taken as the period of metamorphism.

As regards the more extreme metasomatosis and later miner- alization, it would seem that the rocks of the included mass were more favorable to the production and maintenance of channels than the surrounding peridotite, and acted as a vent pipe for the escape of solutions from the more highly heated lower portions of the peridotite mass to the overlying rocks, or possibly to the surface.

In considering the possibility of an origin of the deposit pre- vious to the peridotite intrusion, the close relationship of the distribution of the veins and the present form of the included mass is suggestive. The veins run along in the direction of elongation of the lens and become smaller, less mineral-bearing and play out just before reaching the serpentine in either direction.

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