Tlie Wording of the Madison Lakes. 121 



THE "WORKING" OF THE MADISON LAKES. 



By WILLIAM TRELEASE. 



Every season a greenish- yellow scum occurs in greater or less quantity on 

 Third and Fourth Lakes (Mendota and Monona), during the hot weather of 

 summer, after the water has been calm for a number of days in succession. 

 When but little of it is present, it appears as fine granules suspended in the 

 water, often scarcely visible to the naked eye except as they reflect the 

 light, when they call to mind the dancing motes in a beam of sunlight. 

 Under the influence of a gentle, but continuous breeze, these particles are 

 collected into fleecy masses, and driven ashore, so that they accumulate 

 along the margin of the lake, forming a slimy scum which quickly putre- 

 fies, giving off a very disagreeable odor. During this change, its color 

 changes to a decided blue-green, which stains the pebbles, sticks, etc., over 

 which it is smeared. The appearance of this scum is sometimes spoken of 

 as the working of the lakes, from a resemblance to the collection of a scum 

 on cider, etc. , when fermenting, or, as an American idiom expresses it, 

 " working." 



Usually the scum is seen in small quantity and only attracts attention 

 for a day or two at a time, in midsumm.er, when it collects on the city side 

 of the lake; for a change in the direction of the breeze, or a brisk wind 

 from any quarter usually scatters it in a short time. In the summer of 

 1882, however, the working of the lakes was noticed early in June, and on 

 the 17th of that month enough scum had collected along the city shore of 

 Fourth Lake to prevent boating. The odor which it gave off was notice- 

 able at a distance of one or two blocks from the water. After a few days 

 a change in the wind brouglit relief for a time, but the trouble was renewed 

 at frequent intervals until the middle of November. The first formation 

 of this scum was apparently traceable to the long, shallow bay between 

 Picnic and Second Points, in Fourth Lake, and to the bay at the west end 

 of Third Lake, from which it was scattered by Avinds, and afterward in- 

 creased everywhere. 



In the summer, during calm weather, the water witliin a foot or two of 

 the surface was everywhere filled -with the minute granules ah'eady referred 

 to. In places where counter currents met, as off Picnic Point, these were col- 

 lected in a local surface film. While this appearance lasted the fish in the lake 

 bit very httle. On several occasions white bass were found in large schools 



