400 KANSAS CITY REVIEW OF SCIENCE. 



magnetic axis of a needle, are always greatest with new needles, or thpse which 

 have been freshly magnetized, and hence a needle should never be remagnetized. 

 unless it is absolutely necessary. If a line be run with an old needle, and the 

 needle is then remagnetized, the compass set to the same variation will not in 

 general run the same line. 



These difficulties in compass surveying, are the main source of the constant 

 litigation in regard to boundary lines, and as land becomes more valuable, these 

 quarrels will become more frequent and more expensive, until some rational 

 method of treatment is adopted. It is not saying too much to assert that in each 

 county there is enough money wasted each year in useless litigation over bound- 

 ary lines, to pay for the permanent establishment of a true north and south hne, 

 which would at once settle most of these difficulties. This meridian line being 

 once determined by astronomical methods, and properly marked on stones, and 

 made authoritative by proper legal enactment, would serve as a standard for all 

 time. Then if two surveyors should disagree, it would only be necessary for them> 

 to set their instruments on this line placing the sights north and south, and they 

 would find that the two instruments must be set to slightly different variations in 

 order to run a true north and south line. If a surveyor should find that he could 

 not retrace one of his own lines run the previous year, he would find by setting 

 his instrument on the standard line, that owing to a change in the position of 

 the magnetic axis of his needle, he must adjust to a slightly different variation. 

 We should then learn in a short time what the annual change in the variation is 

 at each county in the State and should no longer be obliged to estimate this 

 change. 



It is certain that all this will be finally done in Missouri, as it has already 

 been done in older States. The only question is, how long will it -take the peo- 

 ple of Missouri to learn that it will pay them to make use of what is well 

 known, and has been practically serviceable in Ohio. It is only necessary for 

 the Legislature to authorize the county courts to employ some competent person 

 to establish such a meridian. There are certainly many persons in the State who 

 are capable of doing such work, and the expense involved is a mere trifle compar- 

 ed with the great benefits to be attained. 



The writer desires to say in conclusion, to any person in the State possessing 

 an engineer's transit, that he will at any time send instructions for the determina- 

 tion of the true meridian, provided that the resulting variation of the needle is 

 communicated to him. 



THE ISTHMIAN SHIP RAILWAY. 



Captain James B. Eads returned to St. Louis on the 9th ult , after a pro- 

 longed visit to Europe on business connected with his well-known scheme for 

 building a ship railway across the Isthmus of Tehuantepec. From his statements 



