AMERICAN. 
JOURNAL OF SCIENCE AND ARTS, 
[THIRD SERIES.] 
Art. XIII.—On the effects of Magnetization in changing the Di- 
mensions of Iron and Steel bars, and in increasing the Intervor 
nology. 
Pane Li. 
(Read before the National Academy of Sciences, in Cambridge, Nov. 22, 1872.) 
On the Elongations and Retractions of Rods of Iron and Steel on 
r Magnetization and Demagnetization. 
To study and measure with precision the minute elongations 
and retractions which rods of iron and steel undergo on their 
magnetization and demagnetization, it is necessary that the 
motions of the part of the measuring apparatus which records 
these changes in aes should not be in the least affected by out- 
side vibrations transmitted to the apparatus, but should be con- 
troled alone by the molecular motions in the rods which take 
Place on changes in their magnetic conditions; also the motions 
of this indicating part of the apparatus should be synchronous 
with the motions in the rods, so that we may be able to study 
e character as well as the amount of these elongations and re- 
tractions, 
Several instraments have been devised by me which fulfill 
these essential conditions, but they were all abandoned (except 
One to be described in detail in Part IV of this memoir), and 
preference given to “The Reflecting Comparator and Pyrome- 
ter’ OF our esteemed colleague, Mr. Joseph Saxton ; this simple 
and precise instrument is well known to American scientists as 
Jour. Sc1.—Turmp Serres, Vou. VI, No. 32.—Aveus?, 1873. 
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