2 Mr. J. L. Drummond 071 a new Oscillatoria. 



ish hue. On lifting some of this in a glass, it seems at first 

 sight quite transparent, but on holding it up to the light, in- 

 numerable minute flocculi are seen floating through every 

 part of it, and producing a mottled cloudiness throughout the 

 whole. 



On examining these under the microscope their nature was 

 at once obvious ; they consisted of excessively fine simple fi- 

 brillar belonging to some species of Oscillatoria. On inquiry 

 among my friends at Glaslough, I found that several theories 

 were entertained respecting the green tinge of the lake, very 

 wide of its true cause : according to one surmise it was owing 

 to some mineral impregnation, probably of a copper mine at 

 the bottom of the water ; and another, equally unfounded, at- 

 tributed it to the drainings of a tan-yard running from the 

 town. 



At first I could only find the plant diffused through the 

 water, as above mentioned; but at length I discovered a wet 

 ditch extending from the lake into an adjoining field, and there 

 it appeared swimming on the surface in large masses several 

 inches in thickness, and above a foot and a half in length. 

 These seemed evidently to be produced by an agglomeration 

 of the filaments floated in from the lake, matted together at 

 the surface and increased in growth. The masses thus formed 

 had a considerable degree of toughness, and were so slippery 

 that they could not be lifted out on the point of a stick. The 

 surface of these masses where dried by the contact of the air 

 was of a bright blueish verdigris hue, while the parts immersed 

 in the water were of a dull opake green. 



That these masses were formed by an aggregation of fila- 

 ments which had previously floated through the lake, but now 

 being freed from the agitation of the waves were allowed to 

 congregate in the motionless water, I would infer from the 

 tendency they show, when undisturbed, to ascend to the sur- 

 face. This tendency I ascertained, not from any experiment 

 of my own, but from the fact, familiar to every inhabitant of 

 Glaslough, that when the water of the lake (which is much 

 used for washing and other domestic purposes) has stood at 

 rest in a vessel for a night or two, a green scum spreads over 

 its surface, which it is usual to remove before use, either by 



