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NATURE 
[¥uly 16, 1885 
As to what may be the cause of earth-tremors I am not pre- 
pared to offer a definite opinion ; but, inasmuch as their associa- 
tion with barometric fluctuations renders it possible that in their 
occurrence they may also be associated with the escape of fire- 
damp, about which we have so little knowledge of practical 
value, it seems impossible that their study should be neglected. 
Whether the results of such a study would be of practical 
value to the miner is not known, but that results of scientific 
value wouid be obtained is indisputable. 
As the making of such observations are neither a matter of 
trouble or serious expense, I sincerely trust that they may be 
undertaken. On some future occasion I hope to describe the 
experiments which I made with one of these instruments on the 
summit of Fujiyama (13,365 feet), where movements were of a 
very marked and decided character. 
Tokio, Japan JouN MILNE 
SOCIETIES AND ACADEMIES 
LONDGN 
Royal Society, June 18. —‘‘ The Removal of Micro-organisms 
from Water.” By Percy F. Frankland, Ph.D., B.Sc., F.C.S., 
Associate of the Royal School of Mines. 
The author has investigated the efficier-7, as regards the 
removal of micro-organisms, of methods of water-purification 
depending upon 
(a) Filtration 
(2) Agitation with solid particles 
(c) Precipitation. 
The method of investigation consisted in determining the 
number of organisms present in a given volume of the water 
before and after treatment, the determinations being made by 
Koch’s process of gelatine-culture on glass- plates. 
Treatment of Water by Filtration,—The filtering materials 
examined were greensand, silver sand, powdered glass, brick- 
dust, coke, animal charcoal, and spongy iron. These materials 
were all used in the same state of division, being made to pass 
through a sieve of 40 meshes to the inch, and in columns of 6 
inches in depth. The following results were obtained :— 
No. of organisms 
in 1 c.c. of Ditto after 
water before filtration 
filtration 
Greensand Soie ese 80 fo) 
ditto (after 13 days)... 8,193 1,071 
ditto (after 1 month) 1,281 779 
Silver Sand ... 11,232 1,012 
Powdered Glass 11,232 792 
Brickdust eAN Snes’ Mest 3,112 732 
ditto (after 5 weeks)... 5,937 406 
Coke Fo) Seq) a8 3,112 fo) 
ditto (after 5 weeks)... 5,932 86 
Animal Charcoal ... very numerous ... fo) 
ditto (after 12 days)... 2,792 ° 
ditto (after 1 month) 1,281 6,958 
Spongy Iron... ... =... 80 ° 
ditto (after 12 days)... 2,792 fe) 
ditto (after 1 month) 1,281 2 
Yhus greensand, coke, animal charcoal, and spongy iron wer 
at first successful in removing all organisms from the water pass 
ing through them, but after 1 month’s continuous action this 
power was in every case lost, the improvement still effected, 
however, by spongy iron and coke was very great indeed, whilst 
the greensand and brickdust were much less efficient, and the 
number of organisms in the water that had been filtered through 
animal charcoal was greater than in the unfiltered water. 
Treatment of Water by Agitation with Solid Particles. —Water 
was agitated with various substances (in the same state of division 
as above) and after the subsidence of the suspended particles, 
the number of organisms in the water before and after treatment 
was determined. 1 grm. of substance was in nearly each case 
shaken up with 50 c.c. of water. The agitation was in nearly 
all cases continued for 15 minutes, but the duratian of subsidence 
was varied according to the length of time whicn it required 
for the water to become clear. The following results were 
obtained :— 
No. of organ- 
isms in 1 c.c. of Ditto after 
water before treatment 
treatment 
Spongy Iron (1 minute agita- x 
tion, 4 hour subsidence ; s{ 609 28 
ANSE LLSECl)) ese ee 
Spongy Iron (15 minutes’ agita- } 
tion, 4 hour subsidence; 5 609 63 
Gea Sed)! ee.wrees Pees al 
halk (15 minutes’ agitation, 5 } 
hours’ Sresidetee ye ae a 8,325 il 
Animal Charcoal (15 minutes’ 8,325 ea 
? 
agitation, 5 hours’ subsidence) 
Coke (15 minutes’ agitation, 48 | Too numerous 
hours’ subsidence)... ..._... J to be counted 
China Clay (15 minutes’ eal 8 ‘Too numerous 
tion,”5 days’ subsidence) to be counted 
In order to ascertain whether subsidence alone would diminish 
the number of organisms contained in the upper strata of water, 
bottles containing infected water were allowed to remain at 
perfect rest, and then the upper layers in the several bottles were 
tested for organisms at different intervals of time. Thus :— 
oO 
No. of organisms 
Hours of rest found in r cc. of 
water 
° 1,073 
6 38 PES 4 6,028 
24 aa = ee 7,262 
48 fe fa0 20 ee ask Pe 48, 100 
Thus, without agitation with solid particles and subsequent sub- 
sidence of the latter, there is no diminution, but on the contrary 
an increase in the number of organisms in the upper strata of 
water. 
Treatment of Water by Chemical Precipitation.—The effect of 
“«Clark’s process”’ in removing organisms from water was inves- 
tigated both in the laboratory and on the large ‘scale. In the 
laboratory experiments the following results were obtained :— 
Organisms 
in 1 c.c. 
Untreated water ... ae is we 85 
ditto (after 18 hours’ rest)... ase 1,922 
Water after Clark’s process and 18 hours’ sub- 
sidence 42 
In a second series of experiments the following results were 
obtained :— 
Organisms 
in T ¢,c. 
Untreated water ... aes cep 205 os6 37 
ditto (after 21 hours’ rest) mae oon 42 
ditto (after 48 hours’ rest)... oe BA 28h: 
Water after Clark’s process and 21 hours’ sub- 
sidence so 507 38 22 
ditto (after 48 hours’ subsidence) 166 
On the large scale the efficiency of the process was examined at 
the Colne Valley Waterworks, Bushey :— 
Organisms 
in 1 c.c. 
Hard water oc oo Bee = aoe 322 
Water after softening and 2 days’ subsidence... 4 
A recent modification of Clark’s process devised by Gaillet and 
Huet was also examined :— 
Organisms 
in rc.c. 
Hard water 182 
Soft water 4 
Thus a very great reduction in the number of organisms present 
in a water may be effected by submitting it to Clark’s process. 
It appears also that the clear water should be remoyed as rapidly 
as possible from the precipitated carbonate of lime, as otherwise 
the organisms may become again distributed through the water. 
Micro-organisms in Potable Water.—The number of organisms 
in natural waters of various origin has been determined by the 
author, who appends the results of a monthly examination, in 
this respect, of the various waters supplied to London during 
| the first three months of the present year :— 
