1897] 



MICROSCOPICAL JOURNAL. 



121 



calculated from experiineiits upon the coetticient of ab- 

 sorption of light by water. The parallelism of the two 

 curves i.s very striking. 



One of the objects of the experiments was to determine 

 the de})th below which the diatoms are unable to develoj). 

 The results show what we should natui'ally expect, that 

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

 turbidity, etc. Thi.s is illnsti'ated by tig. 2, whicii 



K.\l'L.\.N \T1UN iiK 1,1.'; Dl.V^,K.i.H». 

 Kijimx- 1. — Liku ('ocliituatf water locatcii i . Lako Cucliitiiatc, Nov. i'.), l.s'j.j. E.vaiiiiiieil Dec. 9, 



1895. Temperature V^-W. Color o 33. The intensity of light at (liOerent depths wr= 



calculateil ou th<' a».siiBiptiou that a layer of water one foot in ilei>tli absorbs 25 pfr rent I 



the light falling upon it. 

 Fi{;nre 2 — Lake Coi liituate w.iter located in the Clu'stniit Hill l{c.-.ei \'rir ;iijil in l.iiKc i lulntns i 



The curves represent the average of two series, the first tioni Nov. 22 to 2!i, the bpcoi <l 



from Nov. 29 to Dec. !t, 1895. Temperature 411° to 40°. No 1. i '. 11. Res. Color 0..<T. 



No 2. Lake Coihituate. Color 0.33. The l>iatoni> inferred to in both ilia<,'i-anis W( r- 



cliieHv Asleiioiiella and Melosira. 



sliows the results of two series of experiments upon water 

 of the saint.' kind located in Lake ("ochitiiati' and (Mic^t- 

 nut Hill Keservoir. The former iiad a tolor ot t).3o, 

 while tlie color of the 1 itter was 0.87. The tlifl'erence be- 

 tween tiie two series is very striking. In the light 

 colored water tlie glow t lis were heavier and extended to 

 greater depths than in the darker water. 



Carve No. 1 represents the growths in Chestnut Hill 

 Reservoir, and curve No. 2 those in Lake ("ochituate. 



