1889. ] NEW YORK ACADEMY OF SCIENCES. 121 
of men who are competent both to design and to carry out the 
work. 
Another bugbear is, that a possible earthquake may cause the 
destruction of the dam, and that New York and adjacent cities 
will be flooded and destroyed. It is undoubtedly true that the 
breaking of any reservoir cannot occur without damage to prop- 
erty and danger to life; but should such arguments prevail, no 
reservoir would ever be built. 
It can, however, be readily shown that if all the water of the 
proposed reservoir should be suddenly discharged, except that 
which would be held back by the old Croton dam and the Mus- 
coot dam, the increased depth of water at New York would prob- 
ably not be sufficient to overflow the bulkheads, 
Aside from this, the probabilities are in any case all against 
such a break occurring as would allow the whole volume to es- 
cape at once; and with a properly constructed dam, there is no 
reason to anticipate any failure whatever. 
As to contamination of the water by residents on the water- 
shed, that danger can be provided against, as has been success- 
fully done at Rochester and elsewhere. Having gone to the 
great expense of building a conduit of ample proportions to 
transmit all the water of the Croton water-shed, let us not, 
through unfounded timidity, stultify ourselves by failing to carry 
out the scheme in its entirety. 
Pror. A. A. BRENEMAN said: The standing objection to 
storage reservoirs is the sediment of organic matter which col- 
lects in them and acts as a hot-bed for animal and vegetable 
life, which further defiles the water. Such sediment is difficult 
to remove, and the weight represented by a depth of one foot of 
it over a single acre will surprise any one who will make the 
calculation. It has been shown by the late Prof. Nichols that 
the influence of the direct rays of the sun may penetrate, as 
heat, to the depth of thirty-five feet in water. As temperature 
is the principal factor in the decomposition of organic matter in 
these deposits at the bottom of a reservoir, it is evident that 
such a reservoir should be more than thirty-five feet in depth. 
Light, of course, goes deeper, and the changes of temperature 
due to circulation of water probably also extend much farther 
