76 Le Conte on the Coast Islands of California. 
plaints of Ncbraskans in respect to the use of the South Platte 
by citizens of Colorado, are groundless. Within our own boun- 
daries at least, the rights of landed proprietors on the lower 
courses of rivers may be protected by statute, and no time should 
be lost in doing this. 
Several considerable tributaries of the Niobrara enter it 
within the irrigable portion of its valley. These may be used 
for irrigation, each in its own valley, or, if not so used, they go 
to swell the volume of the river and add lai"gely to the aggre- 
gate of acres irrigable from it. My measurement was taken in 
the dry season and should be raised somewhat to obtain the 
average capacity of the river. 
Summing up all these considerations I am of the opinion that 
20,000 acres of land in the Niobrara valley may be irrigated 
now, and that this inay be doubled by the increased rainfall 
which will probably result from irrigation. 
THE FLORA OF THE COAST ISLANDS OF CALIFORNIA 
IN RELATION TO RECENT CHANGES OF PHYSICAL 
GEOGRAPHY. 
BY JOSEPH LE CONTE. 
Some of the results reached by Mr. E. L, Greene in his 
studies of the flora of the islands off the coast of southern Cali- 
fornia^ have deeply interested me, because I believe their ex- 
planation may be found in geologically recent changes in the 
physical geography of California. 
These remarkable islands, eight or ten in number, are strung 
along the coast from point Concepcion southward, and separa- 
ted from the mainland by a sound 20-30 miles wide. They 
are of considerable size (the largest being about 200 square 
miles in extent), and vary in bight from 1,000 to 3,000 feet. 
They have all the characteristics of continental islands, and are 
undoubtedly outliers of the mainland, at one time connected 
1 Studies in the Botany of California and parts adjacent, VI. E. L 
Greene, i — Notes on the botany of Santa Cruz island. Bull.7, Cal. Acad. 
Sci. 
