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Proceedings of the Royal Society 
above a million per gramme. The colonies are of all kinds of fungi, 
more especially aspergilli, bacteria, bacilli, and microccoci. 
Pond Water and open Wells. — A typical open pond which received 
no drainage, and was frequented by ducks and geese, contained 
water which yielded to cultivation 3534 colonies to the gramme ; 
465 of these were bacilli liquefying the gelatin, and 47 were 
bacteria, agreeing in general characters with Bacterium termo. 
An open well in Devonshire gave the following analytical 
values : — * Nitrogen as nitrates, *0984 ; chlorine, 3'2 ; ammonia, 
0014; albuminoid ammonia, '0078; oxygen consumed in 15 minutes, 
*0648 ; oxygen consumed in 4 hours, '1666 ; hardness, 22'9 ; 
total solids, 32*5. The ordinary microscopical examination de- 
tected epithelial cells, vegetable debris, and moving animalcules ; 
35 mgrs. of the water yielded to cultivation 330 centres, 4 of 
which slowly liquefied the gelatin. This is equal to 9428 per 
gramme. 
Canal Water. — The Regent’s Canal, in its course through the 
Metropolis, has been for years little better than a stagnant ditch, and 
the composition of its waters approximates to that of dilute sewage. 
A sample, taken a foot below the surface, gave colonies equal to 
32,352 per gramme ; whilst, just above the mud, another sample gave 
521,739 per gramme. 
River Water. — The water of a stream with an appreciable velocity 
shows the same general fact, viz., more micro-organisms near the 
bottom than the surface; e.g ., samples taken from the Thames at 
Sunbury just opposite the intake of the water companies, yielded to 
cultivation the following figures : — 
Near the surface, 11,050 per grm. 
Close to the bottom, 59,800 ,, 
In the same locality a second sample, taken above some black mud, 
yielded colonies equal in number to 6,430,000 per gramme. 
It thus appears that in canals and rivers the bacteria slowly 
subside, probably by adhering to the mineral and organic substances 
which are continually sinking. That the richness of the bottom 
layer in bacteria is intimately connected with the precipitation of 
particles, is evident from the following experiment : — A wide 
upright glass vessel 2 feet 5 inches in height was filled with sterilised 
In grains per gallon. 
