REPORT OF THE DIRECTOR I917 97 



sandy clay adjacent to bogs through which manganiferpus waters 

 are percolating. At the Gott-Mesick locality (figure 2) at the time 

 the trench was made, the manganese zone illustrated a significant 

 coincidence in this respect. From the upper bog water was running 

 through the zone above the clay as ground water in the direction of 

 the lower bog. Where the manganese was best developed in the 

 form of nodular masses there occurred a water channel from which 

 water flowed out into the trench. It would not seem at all unlikely 

 therefore that the greater development of the manganese in the 

 Gott-Mesick bog was due to the continuous contribution of the 

 manganiferous waters, originating from the upper bog and flowing 

 as ground water to the lower bog. The porosity of the loamy clay 

 of the ridge would naturally furnish excellent oxidizing conditions, 

 a? a result of which the conversion of the bicarbonate to the dioxide 

 might readily take place. 



The ultimate origin of the manganese must be sought for in the 

 rock underlying the drainage basin of the bogs. The bog depressions, 

 of course, act as natural reservoirs for the immediate run-off of the 

 surrounding country, through the various small tributaries. In 

 considering the general geology of the area, it was found that all the 

 manganese bogs were located at about the same general elevation, 

 and that beneath all the bogs the same type of rocks belonging to 

 the same geological horizon occurred. It was the hope of the writer 

 that the ultimate origin or source of the manganese might be trace- 

 able to the associated rock formations with some beds of primary 

 manganese mineral, but no definite evidence in the matter was forth- 

 coming. The chief formations underlying the manganiferous section 

 are the Hudson River schists, and greenish, reddish and purplish 

 slates, all belonging to the Ordovician and the Rensselaer grit of the 

 lower part of the Silurian system. Of course nothing but a petro- 

 graphic examination has been made of these formations in the 

 Hudson valley, so far as the writer is aware, but from their 

 northern occurrences in Vermont and New York the Hudson grits 

 were essentially clastic rocks composed of fragments of quartz, 

 muscovite, plagioclase, chlorite, sericite, quartzite, slate and some 

 carbonate (4: 187). 



The red slates of the slate belt of Vermont and New York, with 

 which the schists of the Hudson river are to be correlated, show as 

 much as 30 per cent Mn0 2 . 



11 Beds of carbonate of a manganese (rhodochrosite) a half inch 

 thick with calcite and quartz occurring in the red Ordovician slates," 

 yielding 32.22 per cent of Mn0 2 , are reported. 



