1897] 



MICROSCOPICAL JOURNAL. 



121 



calculated from experiments upon the coefficient of ab- 

 sorption of light by water. The parallelism of the two 

 curves is very striking. 



One of the objects of the experiments was to determine 

 the depth below which the diatoms are unable to develop. 

 The results show what we should naturally expect, that 

 it depends upon the character of the water. — its color, 

 turbidity, etc. This is illustrated by tig. 2, whicii 



EXl'LAN.\Tll».\ Hi- iiljL DiA^ii-iMa. 



Fi;;U]f L — L.il^e L'ocliituatu water lucutctl i.. Laku CoLhiiiuUi-, ^iuv. li'J, Ib'jj. Kxumiued Dec. 9, 

 1895. Temperature 40°-44°. Color (i :j:j. The iuteusity of light at different depths was 

 calculated on the assumption that a lnyer of water one foot in depth ahsorbs In prr cent t 

 the light falling upon it. 



Kigure 'i — Lake Cocliituate water located in the Chestnut Hill Uesei vi'ir- :ii]d in Luke Cochitua »■. 

 The curves represent the average of two series, the first from Nov. 2i tn 2'.i, the seeoi d 

 from Nov, 29 to Deo. 0, 1895. Temperature 4(1° to -10°. No I. C. H. Res. Culur O.ST, 

 No. '1. Lake i.'oehitnate. Color a..3:i. The Diatoms referred tn iu both diagrams wcr- 

 chietl}' Astei ionella and Mclosira. 



shows the results of two series of experiments u})on water 

 of the same kind located in Lake ("ofhi tuate and Client- 

 nut Hill Reservoir. The former had a color of 0.33, 

 while the color of the litter was 0.87. The difference be- 

 tween the two series is very striking, hi the light 

 colored water the giowths were heavier and extended to 

 greater depths than in the darker water. 



Curve No. 1 represents the growtlis in Chestnut Hill 

 lleservoir, and curve No. 2 those in Lake Cochituate. 



