TORNADO THEORIES. 361 
near a tree, or in a grove during a tornado for fear of being struck by flying 
timber. Occasionally a tornado of great intensity will cut a clean swath through a 
grove, but forests tend to break the force of tornadoes, and will drive most of 
them into the upper air. All towns in prairie States should plant heavy groves 
of hard timber southwest of them. During a residence of forty years in southern 
Michigan when it was heavily timbered, tornadoes were unknown ; that is, they 
were driven into the upper air and rendered harmless, but since the forests have 
been cut away tornadoes in that part of the State have become somewhat frequent 
and destructive. Not to build and protect against tornadoes seems like not tak- 
ing medicine for fevers. Sometimes a fever proves fatal, but most fevers can be 
cured, and so most tornadoes can be rendered comparatively harmless. 
By a careful study of the principles which underlie these storms, and an 
observance of the premonitory signs, during the tornado season, it is believed 
that few, if any persons, who keep their presence of mind and act intelhgently 
and promptly, when the storm appears, need be killed by a tornado. Still it is 
always best to have a clear conscience whatever may happen. 
Meteorologists are carefully studying these storms. The Signal Service already,- 
in their daily reports during the season, indicate the barometric trough of low 
pressure, extending from the southwest toward the northeast, along which torna- 
does move, and it is believed that the time is not far distant when they will pre- 
dict to certain districts probable tornado days. 
Fort Stockton, Texas. 
TORNADO THEORIES. 
In the discussion which followed the reading of Dr. P. R. Hoy's paper upon 
The Tornado at Racine, Wisconsin, May i8, 1883, before Section B of the Amer- 
ican Association for the Advancement of Science at the Minneapolis meeting, 
the following statements and suggestions were made by some of the distinguished 
physicists present : 
Mr. Hoy's paper began by stating that the early part of the day was pleasant, 
but about 6:45 in the evening two clouds of ominous appearance joined, from 
opposite quarters of the heavens, and at once the cyclone began. Its general 
direction was to the north of east. There was no rain at Racine with the storm, 
but there was noticed a very strong odor of ozone while the cyclone was at its 
height. At the start it was barely two rods wide, but when it reached Racine it 
had expanded to twenty rods. Its motion was rotary and oscillatory, and all 
debris was thrown to the centre of the track. When the cyclone crossed the lake 
it formed huge water-spouts, one central, and seven to eight accessory, whirling 
about the main trunk. 
Prof. H. A. Rowland proceeded to discuss the paper as follows : Most ob- 
servers of tornadoes just perceive that there is a whirling motion of the air, and 
t knocks down objects, and that is the principal thing they see. But that is very 
