1886. ] Botany. 1051 
rior region were derived from an original iron carbonate which 
was interbedded with carbonaceous shales which were them- 
selves often impregnated with the same mineral. By a process 
of silicification these carbonate-bearing layers were transformed 
into the various kinds of ferruginous rocks now met with in 
this region. In some cases silicifying waters decomposed the 
iron carbonate in place, producing tremolite or actinolite and 
magnetite, which with the excess of silica remaining formed the 
actinolitic schists so frequently found associated with the iron 
ores. In other cases direct oxidation of the carbonate gave rise 
to bodies of hematite. In still other cases during the silicifica- 
tion of the rocks and the decomposition of the carbonate, the iron 
was removed by leaching and deposited in other places as it be- 
came oxidized. The jasper is supposed to be secondary and to 
have been deposited upon the removal of the iron carbonate in 
the process of silicification. The various theories which have 
heretofore been put forward to account for these interbedded iron 
and jasper layers are all in turn examined and pronounced in- 
sufficient to explain the phenomena met with everywhere in the 
study of the region. 
BOTANY .! 
Tue WIND AND THE TREE-TOPS.—Since 1875 the writer has 
observed, in various parts of the country, 156 instances of injury 
to the trunks or branches of trees by win 
Of all ordinary trees the common red maple appears to suffer 
most in hard winds, and the whole 156 observed cases of injury 
were confined to the various species of deciduous trees, The 
writer has seen hundreds of long-leaf pines in Georgia and Flor- 
ida that had been blown up by the roots, but not one injured in 
trunk or branch while the tree was yet standing. Also close in- 
quiry in Iowa and a whole summer’s observation among the 
white pines of Tennessee failed to reveal a single case in which a 
tree of that species was injured by the wind. Of the 156 ob- 
served instances of injury sixty-one per cent were limbs split off 
at the crotch. 
The crotches of a tree are its weak points. Nature recognizes 
this fact and guards against the weakness by swelling out the 
wood about the points of branching. Notably is this true of the 
white pine. Ina large tree of this species the limbs come out in 
regular whorls about two feet apart. Midway between each two 
successive whorls the central axis of the tree has a minimum 
size. Above and below this point of least circumference the 
Sbe gradually swells out to support the successive sets of 
ranches 
In sixty per cent of the observed injuries the trunk divided 
_ into two or more large nearly equal branches, and one of these 
1 Edited by Professor CHARLES E. BEssEY, Lincoln, Nebraska, 
