NO. 2 PRE-CAMBRIAN ALGONKIAN ALGAL FLORA 87 



Lake is reported to be about 125 feet deep at the deepest part by Mr. C. M. 

 Crouse, of Syracuse, who has sounded it. The rock seen in the ravines at the 

 head of Round Lake was a gray, rather thin-bedded limestone, not much 

 weathered or disintegrated. Fragments of the wall rock are abundant in 

 the drift. 



The region around the valley, judging from the shape of the hills, is 

 morainal. A considerable stream connects the two lakes and flows out from 

 Green Lake through an artificial, straightened and deepened channel which has 

 been cut through a swamp. This ditch cuts through beds of tough white and 

 rather porous calcareous tufa and beds of loose granular marl. Tufa also 

 appears in great blocks on the sides of the principal ravine leading out from 

 the head of Round Lake near the rock outcrops but none was seen in the lake. 

 In Green Lake considerable spaces along the shore have deposits of tufa 

 which extend out into the lake from the shore for as much as twenty feet, or 

 more in places, forming perpendicular or overhanging sub-aquatic cliffs or 

 terraces. These terraces extend from slightly above the surface, at the stage 

 of water when visited, to below the level to which one can see through the 

 greenish, somewhat turbid water. The terraces are covered, wherever ex- 

 amined, with an incrustation of calcareous marly substance, which shows 

 bluish-green wherever it is freshly broken, especially near the surface. This 

 covering layer is, in general, weakly cemented and friable and is easily scraped 

 from the more consolidated portions which it sometimes covers to the depth 

 of an inch or more. This living layer covers not only the rock, but other 

 substances which are in the water, often coating branches of fallen trees 

 to a thickness of one to two inches, while stumps of trees which are favor- 

 ably located often appear like heads of coral near the water surface. 



In two places, logs of white cedar (Thuja) were noted which were com- 

 pletely imbedded in the solid faces of the cliff and projected from them. 

 One of these logs passed diagonally through the deposit, appearing both 

 above and below it. In many cases the dead trees and branches form dense 

 mats on sides of the steep wall of the lake below water level and are apparently 

 in the process of being covered with the algal incrustation, as there are thick 

 deposits of the Hmy matter characteristic of these in many places. It may 

 be that these collections of woody debris form the foundations on which the 

 terraces which have developed have been started. 



Specimens broken from the underlying tufa show a considerable amount 

 of porosity, but the limestone from the terraces is not friable like the incrus- 

 tation, although apparently of the same origin, since some of the twigs in- 

 cluded in it run through both hard and soft material. The under sides of 

 fragments of the compact rock which lie submerged on the surface of the 

 terraces often appear to have botryoidal structure. 



The tufa of the terraces is quite different in appearance and apparent origin 

 from that in the valley below the lake. Chara remains are frequent in the 

 tufa of the ditched level, but none were noted in the material forming the 

 terraces, and no Chara was seen in the lake, except in the outlet, and that 

 was but slightly incrusted with lime. 



The occurrence of the terraces in spots along the lake suggests special 

 reasons for the development of these terraces at certain points, but no such 

 reasons appear from casual examination. A slightly higher level than that at 



