ELASTIC CONSTANTS OF ROCKS. 
61 
uniform in size and of rudely rounded or subangular outline. The quartz 
grains are clear and fresh ; the feldspar individuals, which are abundant, on the 
other hand, are for the most part in an advanced stage of alteration, being 
always turbid and in most cases quite opaque, from the presence of alteration 
products. Some few grains of comparatively unaltered plagioclase are, how- 
ever, present, and scattered through the rock there is a considerable amount 
of hydrated oxide of iron, which often lies between the grains, forming a 
cement. The rock, however, also contains a not inconsiderable amount of 
calcite, which causes it to effervesce slightly when treated with dilute hydro- 
chloric acid, and which is also seen to lie between the clastic grains also form- 
ing a cement, often in the form of individuals of a size comparable to those 
of the other minerals. 
The rock, however, is not a crystalline rock, but a typical clastic one. There 
is not a continuous crystalline web or mosaic, but a mass of rounded or sub- 
angular grains which are in part cemented together as above described, but in 
part are separated by minute open spaces. It is to be expected, therefore, that 
the rock will show serious defects in elasticity, as proves to be the case 
when attempt is made to determine its elastic constants. A photomicrograph 
of the rock taken in ordinary light and multiplied 27 diameters is shown in 
Plate XVI B. 
A square prism of the rock was employed, and it was found to be dangerous 
to submit it to a load of over 4,000 pounds, the crushing weight of the rock 
being much lower than that of the other rocks, which are crystalline in texture. 
The figures obtained are given in the following table: 
Sandstone, Cleveland, Ohio, United States. 
Size 
l.OOOX 1.025 
1.000 
Area 
1.025 
E 
2,290 000 
<r 
.29 
D 
1,816,000 
c 
888,000 
Load (in pounds). 
Longitudinal 
compression 
(multiply 
readings by 4 
for millionths). 
Lateral 
extension 
(millionths). 
I,OOO. . . . 
o 
O 
2,OOO 
I S2 
no 
3.OOO. . 
288 
241 
4,OOO 
3,000 
2 OOO 
426 
309 
ITS 
396 
305 
178 
I OOO 
4. 
o 
