425 



sufficient to trace with accuracy the course of production in 

 Phelps Lake in this year, they yield many suggestions of recur- 

 rent pulses of production similar in duration, though of greater 

 amplitude, to those more clearly defined in channel waters. A 

 comparison of Plates XII. and XLIT. will indicate the presence 

 of pulses of production in both localities, culminating in the ma- 

 jority of instances at approximately monthly intervals. There 

 are eight such culminations in Phelps Lake visible in the rec- 

 ords of March-December, culminating in March, May, June, 

 July, August, September, November, and December. In spite 

 of the disparity in the records in this lake and the river, the 

 similarity in the location of the pulses in the two localities is 

 apparent in all of the above months but August and November 

 — both of which are months of unusual hydrographic disturb- 

 ances in channel waters. 



A detailed comparison in the movement in production in 

 this lake and the adjacent river shows agreement in the direc- 

 tion of movement in 14 out of 21 possible instances, or 67 percent., 

 5 of the 7 exceptions falling in the hydrographic disturbances in 

 August-September and November. In the case of Quiver and 

 Thompson's lakes the problem of comparison is made difficult be- 

 cause the fortnightly collections in Phelps Lake and these local- 

 ities are not upon coincident, but alternate, weeks, and makes the 

 the similarity or difference probable rather than precise. A 

 comparison shows 16 agreements out of a possible 20, or 80 per 

 cent., in the case of Thompson's Lake, and 17 out of 20, or 85 per 

 cent., in the case of Quiver Lake. Both of these lakes are af- 

 fected by hydrographic changes at lower levels which do not 

 disturb Phelps Lake, and we find that 6 of the 7 exceptions oc- 

 cur in the period of floods at low levels. As a whole the move- 

 ments in production in the lake in 1898 agree with those else- 

 where in 47 out of 61 possible instances, or in 77 per cent. In 

 view of the fact that the records cover also the low-water period 

 this is a notable degree of agreement, and is to be attributed 

 to the unusually high average level for the year and to the 

 equalizing effect of high water. This factor is not, however, in 



