SCIENCE 
Fray, SEPTEMBER 27, 1918 
CONTENTS 
Magnetization by Rotation: Dr. S.J. BARNETT. 303 
The Origin of the Pink Bollworm: Dr. C. L. 
URED a Wie 2 -. haere cha dines « occ aerate a miete 309 
PREIESCM NUDES) Sah. re dire Wate elaine whe Uw eu etgete! ate 312 
Scientific Events :— 
The Development of the Dyestuff Industry ; 
_ Health Mission to Italy under Red Cross 
Auspices; Civil Service Examinations 313 
Scientific Notes and News ...........0.0000+ 317 
University and Educational News ........... 317 
Discussion and Correspondence :— 
Red Rays and Photoelectric Effect: Dr. 
CuHEsTER ARTHUR ButTMAN. Special Growth- 
promoting Substances and Correlation: 
CraruEs O. APPLEMAN ...:....00.2 2.00005 318 
Quotations :— 
The Medical Profession in Great Britain and 
MMMM Wot Sein oho afar las cle acdc a erea Thee Seki 320 
Scientific Books :— 
Comstock on The Wings of Iisects: Dr. Z. 
Hem IVEMETNCTATECROY Waite ia peh cate tdi 6 oie erate mie yeha dhe’s Sialg 
The Proceedings of the National Academy of 
Sciences 
Special Articles :— 
The Imbibition of Water by Gelatine: 
Epira BettaAMy SHREVE. Alcoholic Bever- 
ages in Diabetes: Dr. W. E. BurGe ...... 
MSS. intended for ‘publication and books, ete., intended for 
review should be sent to The Editor of Science, Garrison-on- 
Hudson, N. Y. 
MAGNETIZATION BY ROTATION! 
So far as we know at present, a magnetic 
substance, that is a substance whose molecules 
are elementary magnets, can be magnetized 
in two ways, and only two ways: In the 
first place it can be be magnetized by creating. 
a magnetic field in it or putting it in a mag- 
netic field, as has been known for very many 
years; and, in the second place, it can be 
magnetized by simply setting it into rotation 
in a region initially neutral magnetically, and 
both initially and finally neutral electrically. 
It is chiefly with this latter process that we 
are concerned at this time. 
Tn this process, as we shall see, the magneti- 
zation is produced directly by a sort of mol- 
ecular gyroscopic action, which distinguishes 
it sharply from other processes in which 
magnetic fields are produced by rotation, but 
in which magnetization may or may not result, 
according to circumstances. It will be con- 
ducive to clearness to consider briefly some of 
these processes. 
Thus if we take a tube of brass, or other 
non-magnetie substance, electrify it, and ro- 
tate it about its axis, a magnetic field will be 
produced similar in a general way to the field 
which would be produced by winding the tube 
with a coil of insulated wire and passing an 
electric current through it, as Rowland proved 
over forty years ago. So far, there is no mag- 
netization. But if a rod of iron is introduced 
into the tube, and either maintained at rest 
or rotated with it, the rod will become mag- 
netized—not because of its rotation, but be- 
1An address delivered before the National 
Academy of Sciences, April 22, 1918. Most of 
the material presented here is taken from papers 
previously published in Scrence, the Physical Re- 
view and the Proceedings of the National Acad- 
emy of Sciences. Detailed accounts of most of the 
work are given in the Physical Review, 6, 239, 1915, 
and 10, 7, 1917. 
