1890. | RAFTER—BIOLOGICAL EXAMINATION OF WATER. 43. 
I have recently made a number of similar comparative counts with 
the result of uniformly getting a larger number of organisms per unit 
of volume, by the method here described. 
The following table shows a number of counts of samples from 
different localities, and illustrates the variations in number and kind of 
organisms which will be found in various waters. In this table the 
results are grouped in classes to save space, and are the number of 
organisms perc c. as before. 
No. OF SaMPLE. | () | @ | @ |W | @) © | @ | ® | @ | Go) 
Sponge Spicules, I Hs hes Nes Meee ah Newel en ° | uli 
Rhizopods, } fo) 2) | Moe |) oN eetod bn fo) I Dees 
Pneusoriay we es 4 5 2 Gt OGn) iieser ul nonh morro | 11 
Rotifera, . I EL Loh) FOr bec Or le eagt gor | ye) | 3 
Crustacea, PW Gants Wie oN Wa eval fame fy). Gil eon! .o.| “o 
Total Animals, : 7 6°) 6, | Sor! 2a som 1s Teas | a 
Wesmidies,  . . . Ow fame Te 3 Peal 5 fo) I I 
iatemiaces, 9 . | 56) 6 | rz) 2) tg) ae elses arey| 271 35 
Zoospores, . . . |130| 51 | 73 |280 |244 | 88 |2400 | 26 |132 | go 
ilaspiyeee, > | 2s) 4) hl) sh sie ee) 1) 5 
@yanepayces, . . | £5.|,38| 70°| -4 (E57 |Ere ° |) 2e.\ 16 
Alge-Fungi, . . Boh SI} TO. 7168). ese ee oO - 3 2 
Total Plants, . . |200 |102 |160 |287 |478 |260 2456 34 152 143 
Amorphous Matter, | 80] ,: 140 |180 238 |230 | 45 |165 |170 |240 
In these samples (8) is from spring and represents very pure 
water. All of the samples except ‘ (6) and (7) are from water 
supplies and represents waters of medi nality. The large amount 
of Cyanophycee in (5) and (6) might ot _ If in the present state of our 
knowledge lead to the rejection of those two waters as unfit for domestic 
purposes, especially, if continuous observation, extending over two or 
more seasons, showed that such extensive growths occurred frequently. 
In all such cases however a study of the environment would be desirable 
before making a final decision, and I do not wish to be understood as- 
now saying positively that a given sample can be definitely rejected on 
the evidence of the biological examination alone. Of this phase of the 
question I also omit extended discussion here, as I have recently given 
it consideration in a paper before the American Society of Civil 
Engineers. 
Plate 2 is a form for record of results at about one-half the 
size to be used in actual practice. This record sheet may be taken as. 
