BELL SYSTEM SLEET STORM MAP 



115 



indicated in Fig. 1. It is, however, possible with proper data available 

 to economically design the telephone lines so that they will withstand 

 the more frequent storms of an average severity pertaining to the areas 

 in which the lines are to be located. In predicting such average 

 storms in different localities, a sleet storm map reflecting past per- 

 formance as to storms and resulting damage is of material assistance. 

 In 1911 arrangements were made to collect data relative to sleet 

 storms occurring in the territories of the various Associated Com- 

 panies and to graphically indicate the cumulative results of such data 



Fig. 1 



with particular reference to the intensity and frequency of the storms 

 recorded. In so far as possible the collection of these data was made 

 retroactive so that, at least for those sections of the country where 

 storms of a destructive nature had occurred, it was possible to start 

 with an accumulation of reasonably accurate past performance data 

 to which has annually been added very carefully collected information 

 with regard to all subsequent storms of consequence. These data 

 have made possible the preparation of a map, Fig. 2, in which the 

 cumulative effect of storms extending over a considerable period of 

 time is shown by various colors, markings and groupings of pins in 

 such manner that for relatively large areas the future storm exposure 

 to which the telephone plant is likely to be subjected, is indicated. 



