SCIENCE. 



FRIDAY, JUNE 12, 1885. 



COMMENT AND CRITICISM. 



Lieut. Cornavell, who is to cany on the 

 series of latitude observations at the U.S. naval 

 observator}^ referred to in a previous number 

 of Science (vol. v. p. 60), has recently returned 

 from an interview with Professor Oom, the 

 director of the observatory at Lisbon. A list 

 of eleven stars has been selected, and the de- 

 tails of the work have been agreed upon. But 

 two stars will be observed in a night, each star 

 being observed east and west of the meridian 

 before the succeeding star is taken up. Some 

 fifteen or twenty observations of each star will 

 be made during the } T ear. With the exception 

 of a Lyrae, the stars range from the fourth to 

 the sixth magnitude, and the greatest zenith 

 distance at which any star will be observed 

 at Washington is not greater than twelve or 

 thirteen degrees. It is proposed to erect an 

 azimuth mark for testing the stability of the 

 instrument ; and a careful determination of the 

 level will, of course, be made with every obser- 

 vation. 



This question of the variability of latitudes 

 is one of considerable interest. Theoretically, 

 periodical changes of latitude may occur, and 

 an examination of observations made at a 

 number of northern observatories during the 

 past seventy-five } T ears — Konigsberg, Milan, 

 Naples, Paris, Pulkowa, and Washington — 

 appears to confirm the existence of such 

 changes. At Pulkowa, which furnishes the 

 most careful series of observations, a diminu- 

 tion of the latitude of 0.23", equivalent to about 

 twenty-three feet, is indicated between the years 

 1843 and 1872 ; but in all these cases the vari- 

 ations are small, and we must be extremely 

 cautious in ascribing them to actual changes 

 of latitude. A series of observations made 

 at Willet's Point by young engineer officers, 



No. 123. — 1885. 



under the direction of Gen. Abbot, also ap- 

 pears to have some interest and possible bear- 

 ing on the question. By these observations a 

 diminution of ninety-five feet is shown in the 

 latitude since 1880 ; but here, again, it is quite 

 possible that this apparent change may be due 

 to errors of observation. Fergola's plan of 

 making a careful series of observations at pairs 

 of observatories, in about the same latitude, 

 but differing considerably in longitude, will, if 

 thoroughly carried out now, go far towards 

 enabling us to give a definite answer to the 

 question fifty years or more hence. 



The American engineer of May 8 contains 

 an article on the levee system of river improve- 

 ment which demands notice from all who wish 

 the line between fact and fiction to be sharply 

 drawn. The case presented is briefly this : 

 the Mississippi-River commission, in 1883, as- 

 serted that they had restored the levees along 

 the Yazoo front so as to exclude overflow from 

 the head of that basin, and that as a conse- 

 quence the height of flood at Vicksburg was 

 about five feet lower in 1883 than it had been 

 in 1882 ; and upon this assertion of facts the 

 commission based an argument for the general 

 construction of levees along the Mississippi as 

 a means of channel improvement. The flood 

 of 1884 came, and rose three inches higher at 

 Vicksburg than it did in 1882, thereby com- 

 pletely overthrowing all the argument of the 

 commission. 



In the article referred to, ' J. B. J.' quotes 

 from later reports of the commission proof 

 that the commission had not restored the levees 

 along the front in question in 1883, nor had it 

 been done in 1884. Unless the clearly implied 

 charge that this misstatement was wilful is 

 successfully met by the members of the com- 

 mission who signed the report of 1883 (General 

 Comstock did not), it would seem that the 



