BEAVER — DAMS. 
375 
themselves with the smaller amount of labour involved in 
eth building of a stick dam. 
To give some idea of the proportions of a dam, I shall 
epitomise a number of measurements given by Mr. 
Morgan : — 
Eeet 
Height of structure from base line . . . . 2 to 6 
Difference in depth of water above and below dam . 4 to 5 
Width of base or section . . . • =, . 6 to 18 
Length of slope, lower face . . . . . 6 to 13 
Length of slope, upper face 9 . „ . . 4 to 8 
The only other measurement is that of length, and this, 
of course, varies with the width of water to be spanned. 
Where this width is considerable the length of a dam 
may be prodigious, as the following quotation will show : — 
Some of the dams in this region are not less remarkable 
for their prodigious length, a statement of which, in fact, would 
scarcely be credited unless verified by actual measurement. 
The largest one yet mentioned measures 260 feet, but there are 
dams 400 and even 500 feet long. 
There is a dam in two sections, situated upon a tributary of 
the main branch of the Esconauba Liver, about a mile and 
a, half north-west of the Washington Main. One section 
measures 110 and the other 400 feet, with an interval of 
natural bank, worked here and there, of 1,000 feet. A solid- 
bank dam, 20 feet in length, wms first constructed across the 
channel of the stream, from bank to bank, with the usual 
opening for the surplus water, five feet wide. As the water 
rose and overflowed the bank on the left side, the dam was 
extended for 90 feet, until it reached ground high enough to 
confine the pond. This natural bank extended up the stream, 
and nearly parallel with it, for 1,000 feet, where the ground 
again subsided, and allowed the water in the upper part of the 
pond to flow out and around into the channel of the stream below 
the dam. To meet this emergency a second dam, 420 feet iong, 
was constructed. For the greater part of its length it is low, but 
in some places it is two and a half and three feet high, and 
constructed of stick-work on the land, and with an earth 
embankment on its outer face. In effect, therefore, it is one 
structure 1,530 feet in length, of which 530 feet in two sections 
is artificial, and the remainder natural bank, but worked here 
and there where depressions in the ground required raising 
D y artificial means. 
