"SLIDES" IN THE CONEMAUGH FORMATION 



351 



above the well-defined terraces, the city has avoided extending its 

 territory excessively. The connecting slopes have caused Kttle 

 trouble in the business district. This is in part due to the fact 

 that the terrace positions were largely determined by the resistant 

 rock. The removal of slaked shales, grading, and the protective 

 effect of building and paving operations have all helped in prevent- 

 ing serious trouble. In the outlying territory dwellings built on 



Fig. 3. — Walls and steps pushed forward as a result of slide movements. The 

 house in the foreground is in immediate danger. Note jagged edge of broken brick 

 walk leading to house in the rear. As is frequently the case, the sliding masses have 

 produced a terrace-like form, with the vegetation growing on its top but little dis- 

 turbed. Many months were required to produce the foregoing result. 



terrace slopes and on the upper hill slopes are sometimes endangered 

 by shdes, and precautions have to be taken to prevent their destruc- 

 tion. The most effective preventive of trouble is the exercise of 

 foresight, the position a house is to occupy being considered with 

 reference to this difficulty. Sometimes thick retaining walls 

 are built at the time to insure safety. That such walls prove 

 inefficient at times is shown by the accompanying figure. Some 



