The daily progressive-miner., 1916-03-14
EXPERT BIOLOGIST
 GIVES HIS OPINION
CONTRADICTS c MANY REPORTS SENT OUT BY VARIOUS
 ALARAIISTS.

the dhdfla Sdndl VIII not ue SNai- lowed up by an earthquake in the future and that the troublesome slides now being encountered will eventually be conquered and the great waterway made an unquali- fled success, is the opinion of Don aid F. Macdonald, formerly canal geologist and now mining geologlst for the United States Bureau of Mines.
 | Mir. Macdonald, who spent sev- eral years on the Isthmus making a careful study as to fragility of the earth's crust, has just made an official report to the effect that, while through seismic disturbances the whole Isthmus is rising at the rate of three feet every hundred years, this will not necessarily in- 1 jure the canal. As far as he sees, it will merely mean a little ad- ditional expense in the dredging of the big waterway. The cause of this rising, he says, is the sinking of the ocean bottom outside the lsthmian shore waters. Everytime there is a little movement of the ocean bottom, the Isthmus, to be in harmony, joins in. He also sug- gests> that if the rising motion be rapid, then there would be serious danger for the canal, but, that from what has happened in recent geologic time, it may be concluded that the canal is not in any appre- ciable danger from the instability of the Isthmian land. The rising of the Isthmus, however, has been responsible for the many slides that have been encountered, in that the motion of the ground has dislocated and crushed the rocks, leaving them weak and unstable.
 At any rate" said MT. MacDon- aid, ".so far as the digging of the Culebra Cut is concerned, these faults have increased the cost of the canal several million dollars.
 "As to the slides, Culebra Cut is vast ditch that passes through many varieties of rock in the nj, miles of it's length. Some of these are weak and unstable, and where the slopes of the cut were steep and 100 to 300 feet high the weak CT rocks crushed down to flatter slopes. Whenever the slope got flat enough, the sliding stopped. At no time did the engineering staff constructing the canal believe that the slides were a menace to the ultimate completion and success ful operation of the canal, in spite f the fact that at times they were somewhat troublesome. They have made necessary the excavation of about 30,000,000 cubic yards more than was included in the first esti- mates for Culebra cut, but they have not in the past and will not in the future endanger the ulti- mate success of the canal"
 MT. Macdonald calls attention to the fact that one is apt to forget that the greatest variation of atmos- pheric pressure near sea level may be more than four million tons per square mile and that if the adjust ment of atmospheric pressure, in a very large cave or mine lags be- hind any quick increase in atmos- pherlc pressure at the surface, a siderable strain may be added to the roof of such an excavation. Discussing the real cause of the slides, MT. Mcdonald declares that in many cases the immediate cause was the oversteepness and height of the slopes, the blasting and other work attributable only to man. He adds that the geologic conditions were not sufficiently considered in the first plans for digging Cule- bra cut.
 As the strength of the famous Gatun dam has been brought into question on number of occasions. MT. Macdonald refers to it in some length. It was found that the Gatun rocks are relatively solid and compact and suitable for founda- tions for heavy structures. How ever, some writers, even recently. have affirmed that the Gatun rocks would soften into mud when Gatun lake filled, and thus the locks and dam would sink their foundations and be damaged or destroyed. Opin- ions of this sort spring from a vivid imagination and not from facts.
 If the weight of Gatun lake is going to force water into the Gatun formation and cause it to soften into a semi-mud that will allow the dam to sink, then all the islands in Gatun lake and all the hills around it, which are of the same formation, should also have their bases softened the same way. and sink into the depths. Reports l that tho Cafr1n dam and iockc are