182 



SCIENCE 



[Vol. LVI, No. 1442 



England granite says that it is the very symbol 

 of solidity. But New England granites have 

 been stripped by glaciers of every trace of de- 

 cayed rock. They are solid because they are 

 freshlj' exposed. That is not the ease with 

 granites in this western counti'y. 



For instance there is granite in the imme- 

 diate vicinity of Salt Lake City. It seems 

 solid. It is used in building. It will take a 

 polish. But I am told it will not hold a polish 

 more than three or four years, because the 

 crystals have begun to decay. Professor Pack 

 tells me that he has examined granite in this 

 vicinity from the surface to a depth of 800 

 feet below it and found even at that depth 

 that decomposition was in progress, as shown 

 by the clouded appearance of certain crystals, 

 the feldspars, under the microscope. 



The granite of Boulder Canyon is decom- 

 posed on the surface. No one knows, as yet, 

 to what depth. But the geologist has reason 

 to suspect its solidity and must add his objec- 

 tion to those of conservative engineers against 

 the suggestion that the dam be built by blow- 

 ing the cliffs into the canyon. 



The other type of dam proposed is to be 

 built of reinforced concrete. Concrete may be 

 described as a rock composed of minerals 

 which are permanent under surface conditions 

 because they form in that environment. Mois- 

 ture promotes the consolidation of concrete. 

 Age increases its strength. So far as the 

 superstructure is concerned, a geologist must 

 reason that a concrete dam will outlive a rock 

 fill dam. The engineering problem in building 

 a concrete dam is that of excavating to solid 

 foundations. It is, in the judgment of con- 

 servative and experienced engineers, reasonably 

 practicable to do so. But, if the conditions 

 of jointing and decay of the rocks are consid- 

 ered as they should be, it will be the geologist 

 rather than the engineer who shall determine 

 whether they are solid or not. 



The foundations are now being explored by 

 drilling. It is not enough. A drill may bore 

 out a core within a foot of a weak seam and 

 not betray its existence. The preliminary 

 examination will, no doubt, be followed by 

 more thorough investigation and it may be sug- 

 gested that a method of shafts and tunnel be 

 employed. Shafts sunk, one on each side of 



the river, and connected by a tunnel at a depth 

 of a hundred feet below the bottom of the 

 channel, would enable a complete examination 

 of the rock, inch by inch. Weaknesses could 

 be excavated and filled. If they should prove 

 too numerous at one hundred feet, the shafts 

 eould go deeper to a deeper tunnel. Eventu- 

 ally when solid roek was found, the rock above 

 the tunnel could be cut away to the surface, 

 stoped, as miners say, and the stope filled with 

 concrete would form an impervious curtain 

 wall. Working from the bottom up, the bed 

 of the river would be approached and the 

 deeper foundations would- be laid without ex- 

 posure to the risk of floods. It is not the 

 province of the geologist to instruct engineers 

 and I would not presume to, but the suggestion 

 may stand to illustrate the problem of a deep 

 and secure foundation, that the geologic con- 

 ditions demand. 



The Garden of Eden was created some five 

 thousand or more years ago by the building of 

 huge dams of earth to control the Tigris and 

 Euphrates, and so well did those ancient engi- 

 neers execute their task that the beauty of the 

 garden became a tradition of all Eurasian 

 races. The garden endured until the state fell. 

 Subtle forces weakened the quality of its citi- 

 zens as moisture attacks the minerals of the 

 granite. Our engineers can build a dam to 

 endure for thousands of years. What is the 

 endurance of our state? What concrete foun- 

 dations of national character are we laying to 

 cut off the underground activities that would 

 destroy it? 



Bailey Willis 

 Stanford University 



EXPEDITIONS OF THE MUSEUM OF 

 NATURAL HISTORY 



In one of the corridors of the American 

 Museum of Natural History the ofiicials of 

 that institution have hung a map of the world 

 to which labels are attached showing the dis- 

 tribution of its exploring parties and field 

 workers. During the present year a larger 

 number of expeditions have been sent out than 

 ever before. Intensive work is being pursued 

 by each department. 



In the department of geology. Dr. Edmund 

 0. Hovey is at present on a trip through Cali- 



