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is done, there will be no more difficulty in filtration, and that in his opinion the additional filter-beds will not we required.
With this opinion I concur.
lt will be better to spend
money in prevention that in cure. I am moreover doubtful whether
any reasonable area of filter-ped could deal effectively with the
out.
The
water when it is in its extreme condition of turbi lity.
suspended mutter is finely divided clay most difficult to filter
If the filter arrests the clay it rapidly chokes and pe-
comes water-tight. If it is kept so clean as to let the water
pass, then the clay goes through also, I have seen fine clay
pass through four feet of clean sand without any apparent reductio
Only a filter to choked as to let little water pass stopped it.
The choice therefore is between s and C. B incolves
the use of iron-work, is therefore less durable ani more costly
than C, which would be the proper plan to adopt in case of origin-
al construction,
But in the present case the reservoir is in use, and
therefore rapidity of construction pecomes an important element.
Without a service-reservoir it will be difficult to regulate the
rate of filtation, the more so as the filters are supplied not oy a pipe, but by a conduit which cannot be shut off at a moment'd
Project C would, in all probability, be most quickly
notice.
executed.
As to the probable time occupied in construction the Resident Engineer gives no information, though he has doubtless
considered the subject_
I am therefore of opinion that the expenditure of $50,000 should be sanctioned for covering the Albany Service
•