Harshberger on Relation of Ice Storms to Trees. 347 
observations made by the writer, the forest and shade trees 
seemed to be injured in the following order: 1, silver maple 
most injured; 2, weeping willows; 3, Carolina poplars; 4, 
beeches ; 5, elms; 6, hickories; 7, white oaks; 8, plane trees, 
especially the oriental species; 9, Kentucky coffee tree, 
almost not at all; 10, coniferous trees, pines, etc., not at all. 
At Horticultural Hall, Mr. John J. Prentzel recorded that 
a branch of an oriental plane tree, broken off encased in ice, 
weighed fifty-six pounds, and that after the ice had been 
melted off, it weighed nine ounces; a ratio of about I: 100. 
Dr. Swartzlander,* of Doylestown, Bucks County, Pa., 
weighed a twig with ice on and it weighed fifteen pounds. 
After melting the ice, the twig weighed nine ounces, a ratio 
of 1:26. Mr. H. H. Chapman® gives an account of the 
effect of this storm on Staten Island. The trees observed 
were elm, beech, tulip poplar and black oak, which had 
sound limbs broken that were four inches or more in diame- 
ter. White oak alone, according to Chapman, seemed to 
resist serious damage by the greater strength of its branches. 
To calculate the force which caused such destruction, twigs 
were cut transversely and diagrams made of the thickness of 
twig and ice incrustation. Calculating from the relative 
area in cross section, it was found that twigs one-eighth 
inch thick were carrying thirty to forty times their weight. 
In addition to this heavy weight, the trees were subjected 
to high winds, so that in many cases the crowns of trees 
were reduced fully go per cent. 
The second storm of Saturday, December 13, 1902, gave 
the writer an opportunity to test the facts recorded above 
and also to ascertain additional facts of moment. Seven- 
teen species of trees and shrubs growing in the Botanic 
Garden of the University of Pennsylvania, afforded material 
for study. The plan pursued was to cut off a limb, usually 
* Forest Leaves, VIII. October, 1902, p. 168. 
* Forestry and Irrigation, VIII, 1902, p. 130; also Experiment Station 
Record, XIII, p. 1053. 
