134 A. Winslow — Flexibility of Limestone. 



if it is not passed, as hair-like lines of incipient fracture are 

 already observable on the lower side of the slab, near its center, 

 running transversely to the length. The slab in question has 

 been in place about 25 years, and the supporting corner posts 

 have settled in such a way that the bearing of the slab upon 

 them is generally only along one edge or along a part of one 

 edge. The carefully made drawing from which the cut is 

 prepared shows all details so well that further description will 

 be unnecessary. 



The measurements for this drawing were made by the writer 

 assisted by Mr. A. E. Woodward,* late assistant geologist of 

 the Missouri Geological Survey, and the drawing was prepared 

 by the latter. The deflections were determined by stretching a 

 fine wire tightly across the block from edge to edge, and then 

 measuring the space between the wire and the slab at any 

 desired point with the aid of a pair of dividers. The length 

 of the slab, it will be noticed, is 6 ft., the breadth 3 ft., and 

 the thickness 2 inches. The distance lengthwise, between 

 supports, is about 4 ft., and crosswise between 1 and 2 ft. The 

 sag at the center of the slab, along the lines A-B and C-D, is 

 nearly 1|- inches, beneath the two ends, or about -^ of the total 

 length, or about -^ of the distance between the supports. 

 Assuming the curve to be the arc of a circle, the radius of the 

 circle would be about 37 ft. ; or, in other words, a long slab of 

 such marble 2 inches thick, could, under continued stress for a 

 period of twenty-five years, be bent to the form of a circle less 

 than 80 ft. in diameter. 



A more detailed study of the measurements yields other 

 facts of interest. Thus an extreme sensitiveness to stress is 

 indicated by the transverse flexing between points of support 

 close together ; this is shown by the sections along the lines 

 A-C and B-D. Further, it will be noticed that, along the 

 sections A-B and C-D, the measurements indicate convex 

 undulation between the center of the slab and the points B and 

 D, due to a recurving downwards of the end of the slab, 

 which projects beyond the point of support. At the other 

 end, however, the support is nearer the end of the slab, and 

 here the curvature is continuously concave. 



* Died September, 1891. 



