of Edinburgh, Session 1885 - 86 . 
489 
water, 1 c.c. of sewage added, the whole shaken, and then allowed to 
stand for twenty-four hours ; at the end of which time samples were 
taken from the surface, the middle and bottom respectively, with 
the following result : — - 
Colonies per grm. 
Surface, 411 
Middle, . 333 
Bottom, 160 
Sea Water . — In the sea. water around the English coast, the 
water at or near the surface seems to be uniformly richer than at 
deeper depths. 
A sample of sea water, taken off the old Pier at Brighton in July, 
gave the^ following results : — Surface, 50 mgrms. yielded 843 
centres — that is, 16,860 per gramme; while a sample from the 
bottom only yielded 230 per gramme. 
A sample of sea water, taken from the surface of the Yarmouth 
coast in September, gave 14,887 per gramme. Dr Yacher of 
Birkenhead kindly supplied me with samples of sea water, taken 
from the surface and at the depth of 20 fathoms off Holyhead, and 
the number of colonies at the surface gave a very similar result 
while the deep sea sample yielded comparatively few centres.* 
Cultivation of ordinary Drinking Water . — For some time past I 
have made cultivations of all waters analysed by me in my capacity 
of a public analyst, and have now sufficient experience to justify a 
judgment as to the utility and limits of the method. A public 
water supply, derived from flowing rivers, or from any surface water, 
varies as to its composition according to season, the more especially 
as the water has a winter character due chiefly to winter rains, and 
summer character due chiefly to the summer drought. It hence 
follows that a standard of purity, which does not take into account 
natural seasonal variations, cannot be correct. 
The water supplied to London by the West Middlesex and Grand 
Junction Companies is analysed by me month by month, and since 
April have also been submitted to cultivation. The analytical 
results, and the number of organisms per gramme, are detailed in 
* I have to my great regret entirely lost my notes of the numbers, but as 
stated, the general facts agreed with the experiments on the shallower waters 
nearer the coast. 
