ABSTRACTS IO9 



prominent, island-like buttes of quartzite, which rise through the 

 basalt. Among the details noted in the Columbia lava are certain hori- 

 zontal joints which cut the vertical columns of basalt and may be 

 traced for several miles. The large vertical columns of lava when 

 weathered sometimes show that they are composed of small horizontal 

 columns or prisms which radiate from a confusedly jointed central 

 core. The joints which bound the large vertical columns furnished 

 the cooling surfaces for the rock they enclose. The bases or ends of 

 the radiating columns are frequently revealed on the surfaces of the 

 slightly weathered vertical columns by a network of lines resembling 

 shrinkage cracks. A report on the observations outlined above will 

 be published by the United States Geological Survey. 



Old Tracks of Brian Drainage in Western New York. By G. K. 

 Gilbert. 



The glacial Lake Warren occupied the Erie and parts of the Huron 

 and Ontario basins. In the next important stage Lake Erie was 

 established as a non-glacial lake, being separated from the glacial Lake 

 Algonquin at the west and the glacial Lake Iroquois in the Ontario 

 basin. As Warren drained westward and all the lakes of the succeed- 

 ing stages drained eastward, it was inferred as probable that the revo- 

 lution was initiated by the opening of an eastward passage for Warren 

 waters. Such eastward passage was sought and found in western New 

 York. In fact several passages were found, which succeeded one 

 another as the northward retreat of the ice-front exposed lower and 

 lower cols on the north-south ridges which diversify the general north- 

 ward slope of that region. Between the ridges there were lakelets, 

 walled by ice on the north, and these lakelets received the material 

 scoured out by the waters in crossing the ridges, so that the surviving 

 phenomena are chiefly channels and scourways through the higher 

 lands, with gravel deltas at their eastern ends. Most of the drainage 

 lines descend to the Iroquois level, but some terminate at higher levels, 

 and it is thought probable that for a short time a glacial lake occupied 

 the middle Mohawk valley, being doubly dammed by ice lobes on the 

 east and northwest. 



The district traversed by the channels extends from Le Roy to 

 Chittenango, and the relation of the channels to one another and to 

 the Iroquois shore show that during the channel epoch the trend of 

 the ice-front in that region was approxinjately east-west. 



