20 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
greatest distance from the Mono Craters at which the dust was 
observed, was in the Humboldt Cajion, about two hundred miles 
northward of the point of eruption. 
At three localities in the Lahontan Basin the bones of extinct 
mammals were found closely associated with the deposits described 
above, thus furnishing the suggestion that the showers of fine vol- 
canic dust were, at least to some extent, fatal to animal life. 
Mr. ANTISELL said it was useless to look for the source of vol- 
canic dust in existing volcanoes on the land. Pumice in the 
character of fine particles, as exhibited, is exclusively the product 
of submarine eruption. Other remarks were made by Mr. Harx- 
NESS. 
Mr. Lester F. Warp read a paper entitled 
SOME PHYSICAL AND ECONOMIC FEATURES OF THE UPPER MIS- 
SOURI SYSTEM, 
in which he described the process by which the valleys of the Lower 
Yellowstone and Upper Missouri are formed, and pointed out the 
importance and the feasibility of utilizing the water of these rivers 
for purposes of irrigation.* 
Mr. GILBERT said that Mr. Ward’s description of the process 
by which the Missouri constructs its flood plain was verified by a 
nearly identical group of phenomena observed by himself on the 
lower course of the Colorado. Mr. Exxiorr concurred with the 
speaker’s view that the system of irrigation should be inaugurated 
by national action rather than local. Mr. Ritry was of opinion 
that the proposed plan of irrigation was entirely feasible, and said 
that the final solution of the grasshopper problem lay in the culti- 
vation of the northern plains. 
Mr. BurcHarp said that while the political advantage of a con- 
tinuous belt of settlement uniting the Atlantic and Pacific States 
was undeniable, he questioned the advisability of increasing at 
present our agricultural production. 
* This paper was subsequently separated into its two natural divisions, 
and the part relating to the ‘‘ physical features ’’ was published with illus- 
trations in the ‘‘ Popular Science Monthly ’’ for September, 1884 (Vol. XXV, 
pp. 594-605), while that relating to the ‘‘economic features’”’ appeared in 
‘‘Science”’ for August 29, 1884 (Vol. IV, pp. 166-168). 
