KANSAS: ©LT wy 
REVIEW OF SCIENCE AND INDUSTRY, 
A MONTHLY RECORD OF PROGRESS IN 
SCIENCE, MECHANIC ARTS AND. LITERATURE. 
VOL. -IV. APRIE 188i. NO. 12. 
lebral YOS IGS) 
THE MAGNETIC SURVEY OF MISSOURI. 
BY FRANCIS E. NIPHER, PROFESSOR OF PHYSICS IN WASHINGTON UNIVERSITY. 
During the summer of 1878, the writer began a magnetic survey of Missouri. 
The object to be attained in sucha survey is to determine the variation of the 
needle from due north, the dip of the dipping needle, and the intensity of the 
magnetic force, at properly selected localities in the State. In field work of this 
kind, it is not possible to attain the same accuracy that is realized in an observa- 
tory, as the mean daily position of the needle varies considerably (two minutes, 
and often more) from day to day. Hence observations are usually made for five 
or six days at each station, and the mean value is taken. 
Believing that there was something to be learned in regard to local effects, it 
was our plan to establish a much greater number of stations of observation than is 
customary, and this made it necessary to spend correspondingly less time at the 
individual stations. This makes the station values less weighty, severally, but, by 
reason of their greater number, it was thought that the value of the work for 
general discussion would not be impaired. Hence, as a rule only one or two ob- 
servations of variation were made ata station unless the result was an unexpected 
one, or unless we had reason to be dissatisfied with the work. 
The apparatus used for determination of the variation (or declination) of the 
needle, consists of a transit of considerable magnifying power and provided with 
a good horizontal and vertical circle, reading to the half minute. This transit is 
mounted on a stand which also carries a small box in which the magnetic needle 
is hung upon a long silk fiber. This needle is of unusual form, being a small 
IvV—48 
