Septembes 27, 1907] 



SCIENCE 



403 



easionally found in the deposits. "VThen- 

 ever the Potsdam sandstone is found in 

 contact with the ore, the lower layers show 

 a deep iron stain, evidently the effect of 

 impregnation by the iron-bearing solutions. 



The fourth class of iron ores, the limon- 

 ites, are not of much importance in the 

 Adirondack region. The deposits are, as 

 already stated, superficial accumulations 

 due to the washing and leaching of the 

 neighboring rocks and soils. They seldom, 

 if ever, exist of sufficient size and richness 

 to repay working, at least under present 

 conditions. 



On Tuesday an excursion to Keesville 

 and the Ausable chasm was made by train 

 and tally-ho. Professors Woodworth and 

 Gushing showed the party the marine delta 

 of the Ausable river, the former lake shore- 

 lines, the post-Hochelogan gorge of the 

 Ausable river cut in Potsdam sandstone, 

 the Potsdam conglomerate, the northern 

 slope of Trembleau mountain, and the 

 anorthosite. 



In the evening at the Champlain Club 

 Professor H. P. Gushing discussed the evi- 

 dences of physical oscillations during the 

 Gambro-silurian in northeastern New York 

 as brought out by a general study of the 

 stratigraphy of the region. There was a 

 great Potsdam subsidence on the northeast, 

 diminishing to zero westward. The suc- 

 ceeding Beekmantown depression en- 

 croached further on the land than did the 

 Potsdam on the southern margin of the 

 region, but like that was greatest on the 

 northeast. During the Beekmantown oc- 

 curred an uplift which caused cessation of 

 deposition in all the region except the 

 eastern border, confining the later Beek- 

 mantown and the Ghazy deposits to that 

 district. Oscillation then occurred between 

 the Beekmantown and the Ghazy, pinching 

 out the Ghazy to the south. Depression 

 then ensued on the south and west, and the 

 Lowville beds were deposited. The Black 



Kiver limestone followed, this being the 

 first formation found on all three sides of 

 the region, which indicates connecting 

 waters and similar conditions on these 

 sides. 



In the following Trenton time it seems 

 likely that the waters nearly overspread 

 the entire present Adirondack region, 

 though shoreline conditions and small sub- 

 sidence are characteristic of the Mohawk 

 valley region. 



Utica shale conditions came in from the 

 east, and gradually encroached westward 

 on the Trenton, so that the one thickens 

 as the other thins, the Trenton thickest on 

 the west, the Utica on the east. Follow- 

 ing the Utica came the uplift which 

 brought most of the region above sea- 

 level. 



On Wednesday, July 10, the party re- 

 gretfully bade good-bye to the hospitable 

 authorities of the Catholic Summer School, 

 and took the delightful sail down Lake 

 Champlain. 



At Baldwins, the steamboat terminal at 

 the northern end of Lake George, the party 

 were met by Professor J. F. Kemp, by 

 whom they were guided in the Lake George 

 valley. The first stop Avas Hague, where 

 the gi-aphite bed at the Lakeside mine was 

 studied. The bed is ten feet thick, and 

 consists of a graphitic schist in which 

 graphite supplies the micaceous mineral. 

 Feldspar, quartz and a little pyrite con- 

 stitute the associated minerals. In phys- 

 ical aspect -the beds appear but slightly 

 changed from a shaly sandstone. The 

 floor and roof rocks are a garnet-feldspar 

 gneiss with much sillimanite. The peg- 

 matitic phases are frequent. The several 

 methods of origin, organic; hydrocarbons 

 akin to petroleum ; the influence of erup- 

 tive rocks, etc., were passed in review. The 

 forms of occurrence of graphite in the 

 Adirondacks, in crystalline limestones, 

 pegmatite veins, and schists or quartzites 



