310 



the days of maximum production were not touched in our col- 

 lections. The meteoric character of the vernal pulse of 1$98 

 in channel waters (PI. XII.) is indicative of such a possibility. 

 If a greater production than that recorded did occur, it prob- 

 ably fell between the 17th and 24th — a period of non-interfer- 

 ence by flood and of rising production. 



The location of the apparent maximum in this year is sig- 

 nificant. This was an early spring, the average of the surface 

 temperatures in April in 1896 (see p. 171) being from 4°to° 11° 

 higher than that in any other April represented in our records. 

 The temperature of 70° degrees is attained almost a full month 

 earlier in 1896 than in 1898 (cf . PL X. and XII. ). The maximum 

 production was recorded in 1898 on May 3; in 1896, on April 

 24, nine days earlier, and it may have antedated even this. 

 Early spring thus affects the life in water much as it does 

 that upon land. Vegetation bursts into leaf and insects mul- 

 tiply in field and forest in proportion to vernal rise in tempera- 

 ture; so in lakes and streams, in like response, the algae multiply 

 with meteoric rapidity, and the animal planktonts dependent 

 on them follow in their wake. In 1896 the early vernal rise 

 in temperature deflects the maximum of the vernal pulse to 

 an earlier date by virtue of this response on the part of aquatic 

 life to the environing factor. 



The average production in April in 1896 (5.67) exceeds 

 that in any other year of our records, in large part, it seems, 

 because of the early spring and the deflection into that month 

 of the maximum production, which in other years passed un- 

 detected or fell in the following month in consequence of la- 

 ter vernal rise in temperature, as in 1898. 



The May pulse has a duration of 31 days, — from the 1st to 

 June 1, — with a maximum amplitude of 3.56 cm. 3 on the 13th. 

 Its mean falls on the 15th, 22 days after that of the preceding 

 pulse. There is in this month considerable hydrographic dis- 

 turbance — a total movement of 7.5 ft., consisting of a fall of 

 3.1 ft. followed by a rise of 4.4. The maximum production oc- 

 c urs during the decline in the earlier weeks, which is practi- 



