206 Rhodora [NOVEMBER 
from the exclusion of the salt water and tidal wash, it is practically 
the same to-day as of old, the fact which affords its chief biological 
interest, most of the salt marsh bordering the river having been trans- 
formed for park, building and other purposes. 
The marsh is on.the left or west bank of the river and is well 
defined. It has approximately the form of a segment of a circle, 
the chord or straight side running north and south, directly east of 
Cambridge Cemetery and close to it, a bank some 20 or 25 feet high 
descending from the Cemetery to the marsh. This bank extends 
from the south end for some two-thirds of the distance, the remaining 
portion of the marsh being bordered by land several feet above the 
marsh and by a hill. The eastern portion of the marsh, forming the 
arc, borders on the river. "The greatest length of the area is 2250 feet, 
or a little less than half a mile, while the greatest width is 800 feet or 
about one sixth of a mile. 
It was in the fall of 1908 that the river was closed. To quote 
from the Sixth Annual Report of the Charles River Basin Commission, 
published December 1, 1908, * On Oct. 20, 1908, the eighty-two gates 
in the shut-off dam, described in the Commission's last report, were 
closed simultaneously. * * * * 'The Basin in the beginning had to be 
filled for the most part with salt water, the long drought having 
reduced the daily flow of the Charles River to so small an amount 
that to fill it with fresh water would have taken many days, whereas 
it was possible to fill the Basin in a few hours with water let in through 
the sluices. "The permanent water level, established soon after the 
closing of the shut-off, is at the grade of 8 feet above Boston Base, 
and Boston Base is 0.64 of a foot below mean low-water mark. * * * * 
Seventeen and one-half miles of shore line have undergone a trans- 
formation which will render their further improvement a matter of 
small expense compared to the cost of their treatment." And again, 
" On the morning of October 20, forty-one men with axes were assigned 
to their stations on the frame from which the gates were suspended, 
and each man was instructed on a given signal to cut the ropes that 
held two gates, after which he was to come down, fasten the gates in 
place with wedges and see that each gate was completely closed. At 
11 4. M. the signal was given and in two seconds all of the gates were 
down; in two minutes they were all wedged securely in place. * * * * 
A large plant immediately began the work of placing earth fill next 
the shut-off dam. Within a week the fill was well up to ordinary high 
