Mathematical and Physical Papers. 245 



A BIT OF ENGINEERING AT MOUNT VERNON. 



By M. L. Ward, Ottav/a University. 



np HE mansion at Mount Vernon is about one-fourth of a mile 

 -■- from the Potomac river and about 150 feet above it. For 

 about 400 yards from the river towards the mansion there is a 

 wooded slope, crowned by a precipitous bluff from ten to fifteen feet 

 in height. This bluff is about 100 yards from the mansion. This 

 slope extending along the river is the deer park. In this park 

 there have been many landslides, from time immemorial. Great 

 masses of earth would become detached from the bank and slide 

 down toward the river. This is shown by the uneven surface of 

 the deer park. In 1903 occurred an immense landslide directly 

 between the mansion and the river. Large masses of earth extend- 

 ing from the middle of the hillside even to the brow slipped down 

 to the sea-wall which has been constructed to protect the bank 

 from encroachments of the river. Repetitions of this slide would 

 destroy a portion of the lawn and soon endanger the mansion. If 

 possible they must be prevented. In May, 1903, the superintendent, 

 Mr. H. H. Dodge, and the writer of this paper examined the 

 locality, and we agreed that drainage only could solve the problem. 

 Mr. J. A. Archer, a mining engineer, became interested in the 

 matter, and I quote at length his account of work, which he kindly 

 furnished me : 



"An investigation of the serious condition at Mount Vernon, 

 caused by landslides, was begun in May, 1903. These slides threatened 

 the entire deer-park front, from the entrance gate to a point some 

 200 feet southwest of the old tomb, a total distance of about 800 

 feet. It was found that back from the Potomac river a distance of 

 300 feet, and 50 feet above the river level, a series of springs and 

 marshy places occurred. One of these springs showed a daily 

 flow of about 3000 gallons and another 2500 gallons. It was de- 

 cided to make a series of borings to determine the general forma- 

 tion, with a view of establishing the levels of these different water 

 veins. It was found that all the springs and 'weeps' came out on 

 a bed of blue clay of twelve feet to fifteen feet in thickness, under 

 which was another water-tight red clay of thirty feet^in thickness ; 

 then five feet of sandstone to river level. Resting on this blue 

 clay, fifty feet above river level, was a bed of water-bearing sand 

 that showed varying thickness from five to fifteen feet. Through 



