314 



SCIENCE. 



[Vol. XX. No 513 



SCIENCE: 



Published by N. D. C. HODGES, 87; Broadway, New York. 



Subscriptions.— United States and Canada $3,50 a year. 



Great Britain and Europe 4.50 a year. 



To any contributor, on request in advance, one hundred copies of the issue 

 containing his article will be sent without charge. More copies will be sup- 

 plied at about cost, also if ordered in advance. Reprints are not supplied, as 

 for obvious reasons we desire to circulate as many copies of Science as pos- 

 sible. Authors are, however, at perfect liberty to have their articles reprinted 

 elsewhere. For illustratioos, drawings in black and white suitable for photo- 

 engraving should be supplied by the contributor. Rejected manuscripts will be 

 returned to the authors only when the requisite amount of postage accom- 

 panies the manuscript. Whatever is intended for insertion must be authenti- 

 cated by the name and address of the writer; not necessarily f -^r publication, 

 but as a guaranty of good faith. We do not hold ourselves responsible for 

 any view oropinions expressed in the communications of our correspondents. 



Attention is called to the "Wants " column. It is invaluable to those who 

 use it in soliciting information or seeking new positions. The name and 

 address of applicants should be given in full, so that answers will go direct to 

 them. The " Exchange " column is likewise open. 



STATISTICS OF THE MISSISSIPPI RIVER. 



ET H. L. WHITING, WASHINGTON, D.C. 



Persons familiar with the range of tide along the seaboard can 

 hardly realize how much the waters of our great interior rivers 

 are affected by the rainfalls and watershed upon and from the 

 vast surrounding valleys. The records of the Mississippi River 

 Commission give much relevant data in regard to these phe- 

 nomena. The following figures have been selected, from the 

 voluminous reports of the Commission, to give more briefly a 

 knowledge of facts that do not come before the general public. 

 As an instance of the great rise and fall of the Mississippi River 

 at Cairo — at its confluence with the Ohio — in the spring of 1891, 

 at its low-water stage, the surface of the river was within a few 

 inches of the top of the levee that protects the city of Cairo from 

 inundation, and frooi the deck of the steamer the writer looked 

 down into the streets of the city several feet below the line of the 

 water rushing by with a velocity of nearly seven miles an hour. 

 In the fall of the same year, at the low-water stage of the river, 

 the steamer, at the same place, was fifty-one feet below the eleva- 

 tion at which she floated six months before; and this was not the 

 greatest range of the river at this point. 



Difference between highest and lowest water-readings. 



Mississippi River. 



St. Louis, Mo 37.1 feet. 



Cairo, 111 53.2 " 



New Madrid, Mo 41.4 " 



Memphis, Tenn 34. 5 " 



Helena.Ark 48.0 " 



Mouth of White River, Arlj 48.4 " 



Greenville, Miss ' 40.8 " 



Vicksburg, Miss 51.1 " 



Natchez, Miss 49.9 '• 



Mouth of Red River, La 48 5 " 



Baton Rouge, La 36.0 " 



Plaquemine, La . 29.9 " 



College Point, La %i.l " 



Carrollton (New Orleans) 15.9 " 



Atchapalaya River, 



Sitnmsport, La 38.8 " 



West Melville, La 80.4 " 



Red River. 



Shreveport, La 25,5 " 



Alexandria, La 40.2 " 



Barber's Landing, La (Head of Atchapalaya) , 51.1 •' 



Arkansas River. 



Little Rock, Ark 31.0 " 



Pine Bluff, Ark 29.5 " 



White River. 



Jacksonport, Ark 33.9 feet. 



Clarenden, Ark 88.8 " 



St. Francis River. 

 Wittsburg, Ark 44.9 " 



Tennessee River. 



Florence, La 30.4 " 



Chattanooga, Tenn 54.0 " 



Cumberland River. 

 Nashville, Tenn 55.6 "• 



Ohio River. 



Paucha, Ky 54.2 " 



Cincinnati, Ohio 69. 1 "■ 



Louisville, Ky (Upper) 45.5 " 



Louisville, Ky (Lower) 71.0 " 



Areas of Overflow. 



St. Francis Basin, Commerce, Mo., to Helena, 



^^j^ (east side of river) „ „„„ <\ 2,874 sq. miles. 



(west side of river) ' ] 3,216 " 



Illinois, Kentucky, and Tennessee 616 " 



White and Arkansas Basins (west side of river), 



Helena to Arkansas City 956 '' 



Yazoo Basin (east side of river), Memphis, Tenn., 



to Vicksburg, Miss 6.648 " 



Macon, Boeuf, and Tennessee Basins (west side 



of river), Arkansas City to Red River 4,955 " 



East side of river, Vicksburg to Baton Rouge. .. 415 " 

 Atchapalaya Basin (west side of river). Red 



River to Bayou La Fourche ... 6,085 " 



Pontcharlrain Basin (east side of river). Baton 



Rouge to Gulf of Mexico 2,001 " 



La Fourche Basin (west side of river), Donald- 



sonville to Gulf of Mexico 3.024 " 



29,790 

 Nearly thirty thousand square miles, or three and a half times 

 the area of the State of Massachusetts. 



Although, as stated, the high-water depth of the Jlississippi 

 River at Cairo is over fifty feet, the low-water depth, on shoals 

 and bars, does not exceed four feet. This great highway to the 

 ocean is, therefore, at these latter seasons, practically unavailable 

 for navigation. Ten of the large ."iteamers of the Anchor Line, 

 which ply between St. Louis and New Orleans, are now laid up, 

 while the elevators of St. Louis have accumulated some nine 

 million bushels of wheat, waiting transhipment.' This is but a 

 partial showing of the importance of the improvement of the Mis- 

 sissippi River, in its low-water navigation, to the commercial in- 

 terests of the country; aside from the injury to agricultural inter- 

 ests from the overflow of the lower basins of the river. 



ON THE USE OF THE COMPOUND EYES OF INSECTS. 



BY R. T.. LEWIS, EALING, ENGLAND. 



Few subjects connected with the study of insects have giveo 

 rise to more widely differing opinions than the rationale of their 

 complex organs of vision, the physical structure of which pre- 

 sents to us one of the most elaborate optical combinations to be 

 found in nature, and this, too, upon a scale so minute as to require 

 no ordinary skill on the part of the microscopist to unravel its 

 marvels. 



Attempts to work out the problem as to what is the impression 

 produced upon the consciousness of an insect by an arrangement 

 so complicated have seldom resulted in satisfactory conclusions, 

 not a few failures in this respect apparently being due to inade- 

 quately clear conceptions as to the application of the laws and 

 phenomena of refraction to the cases in point. But whether the 

 subject is approached from the standpoint of those who regard an 

 organ as having elaborated itself in obedience to the necessities of 



' November, 1892. 



