August 29, 1884.] 



SCIENCE. 



167 



guarantee the ultimate settlement of the eoun- 

 try to an}' required degree of densit}'. I speak 

 of the valleys of these rivers, because it is along 

 these that railroads are either already con- 

 structed, or are soon to be constructed ; and 

 also, because, whatever ma}' be the case else- 

 where, a large part of these valle}'S far above 

 the flood-line is alluvial in character, and highly 

 fertile. 



Now, in comparing this region once more 

 with that of the Upper Platte, whether with the 

 south fork in Colorado, or with the north fork in 

 Wyoming, one great distinguishing fact of the 

 utmost importance presents itself. This fact 

 is, that while, if every drop of the water that 

 flows in the Platte and its tributaries could be 

 turned upon the land, it would only irrigate a 

 small fraction of its own valley, we have in the 

 Missouri and Yellowstone, even in August, a 

 volume of water large enough, if economically 

 applied to this object, to convert the whole of 

 the arable land lying adjacent to them into a 

 rich agricultural region. 



Major Powell and his able assistants have 

 carefully calculated the relation of water-supply 

 to irrigable territory ; and they come to the con- 

 clusion that in Utah a flow of one cubic foot 

 per second will irrigate one hundred acres of 

 land. If this should prove a low estimate for 

 Utah, where evaporation is so rapid that it 

 dries up large rivers almost in their course, 

 it would certainly be -ample in the region of 

 Chinook winds. 



The volume of water carried by the Upper 

 Missouri and Yellowstone for that part of their 

 course of which we are speaking has not been 

 definitely ascertained. The average annual dis- 

 charge of the Missouri River at its mouth was 

 determined by Humphreys and Abbott at 120,- 

 000 cubic feet per second. A measurement 

 was once taken at the source of the Upper 

 Missouri, i.e., at Three Forks, at a time when 

 the river was found to be four feet below high 

 water, and eight inches above low water, when 

 the volume was found to be 8,541 cubic feet 

 per second. Between these two great ex- 

 tremes we are compelled to estimate for our 

 present purposes'. Perhaps 50,000 cubic feet 

 per second would not be an excessive estimate 

 for the volume of the Missouri below the mouth 

 of the Yellowstone ; or, assuming, as is claimed, 

 an equal volume for each branch, 25,000 feet 

 each for the two rivers above their junction. 

 The calculation should not be based upon low 

 water, since little use can be made of water in 

 August and September, when the rivers are low- 

 est ; while it is in May and June, when the water 

 is still high, that irrigation is chiefly required. 



Each of these rivers, could all their water be 

 utilized, would irrigate, at the above estimate, 

 2,500,000 acres, or nearly 4,000 square miles. 

 This average would hold for points higher up ; 

 since the supply of these streams from their 

 tributaries scarcely exceeds the evaporation, 

 and the Missouri is not much larger at Fort 

 Union than at Fort Benton. The distance 

 between these points, hy the windings of the 

 river, is 669 miles. If the valle}' of this river 

 could be irrigated to a width, on an average, of 

 two miles, this would make, at the most, less 

 than 1,400 square miles of surface. This, how- 

 ever, would be reduced in man}' wa}'s. The 

 smaller curves would be straightened. Much 

 of the way the valley is narrow, and for long 

 stretches, especially in the upper portion, it is 

 reduced to a mere canon : 1,000 square miles, 

 or 640,000 acres, would be a large estimate 

 for this portion of the Upper Missouri, which 

 certainly would not require more than half of 

 the available water. The same would be true 

 of the Yellowstone ; and thus, after thoroughly 

 irrigating their own valleys, these great rivers 

 might, should this be found practicable, furnish 

 large quantities of water, to be conducted from 

 points near their elevated sources to other out- 

 lying fertile tracts, which would also become 

 the centres of a wide-spread and thrifty popula- 

 tion. 



To this scheme, I am aware, mam* minor 

 objections may be raised, such as the destruc- 

 tion of navigation, about which there would be 

 differences of opinion, but especially respecting 

 the method by which it could be put into prac- 

 tice. This latter question, neglecting all de- 

 tails, we may now briefly consider in its most 

 general aspects. 



It is in the nature of things, that the settlers 

 themselves of the districts in question can 

 never carry out this extensive system of irri- 

 gation. To be made a practical success, it 

 would require an immense outlay of capital. 

 The few who will go there, knowing that no 

 such S3*stem exists, could never afford to in- 

 augurate it. The effect of its not being done 

 must be to prevent its ever being done : there- 

 fore, under the ordinaiy laws of supply and 

 demand, it can never be accomplished ; yet no 

 one in this age of great engineering enterprises 

 will den}* the physical possibility of such a 

 scheme. Scarcely any one, probably, could 

 be found to question its importance. It must 

 be clear to all, that, if the means of readily 

 irrigating these lands existed, that country 

 would be rapidly filled up by a thriving agri- 

 cultural population, which would bring after 

 it its customaiy train of civilizing agencies. 



