vo7i Schrenk — A Severe Sleet- storm. 145 



ice-laden trees break so much more readily when the wind 

 blows than on a still night, a fact familiar to most people. 

 The wind velocities were not high during the storm period 

 and on the following day. At 7 p. m. of Feb. 27th, it 

 was 20 miles E., dropping to 17 miles during the night, and 

 14 miles N. by the morning of Feb. 28th. The extreme 

 velocity on Feb. 28th was 31 miles N. 



How great the weight was which was borne by the branches 

 can perhaps best be seen from the accompanying photographs 

 (upper figures, PI. X, XL ), made on the morning of February 

 28th. The first one represents a group of hornbeam trees 

 ( Carpinus belulus) in the arboretum of the Missouri Botanical 

 Garden ; the second is a view on Flora avenue, a street extend- 

 ing east and west from the Garden ( the photograph was taken 

 looking to the east). The branches of the hornbeams trailed 

 on the ground, and the tops of the small maple scraped on 

 the snow of the street. It was impossible for one person to 

 lift the top of the maple, much less to restore it to its origi- 

 nal position. These trees are good instances of the appear- 

 ance of the trees all over the affected area. 



Some 200 branches, taken from various trees, were weighed, 

 when covered with ice, and after the same had melted, to 

 determine what weights the trees were able to withstand. 



CD 



Some of the results are given in the accompanying 

 table. Something must be said about the distribu- 

 tion of the ice on the branches, before referring to 

 the table. Vertical branches became coated with a layer 

 of ice of equal thickness on all sides. After a time as the 

 rain fell on the ice-coated twig, it flowed down and as the 

 wind swayed the twig back and forth more ice was deposited 

 at some points than at others. A thicker layer formed on the 

 side from which the storm came ; in some cases this was twice 

 as thick as on the opposite side. If the branch was a strong 

 one it bent but slightly under this added weight, and by the 

 next morning it appeared as a long rod coated with a layer 

 of ice varying from f— |- inches in thickness, in some cases 

 even more. The great majority of branches are not vertical, 

 but are inclined one way or another. The rain fell on the 

 upper side and froze in part, while some dripped from the 



