REPORT OF THE CHIEF ASTRONOMER 55 



SESSIONAL PAPER No. 25a 



The carbon dioxide shows some deficiency if, as seems necessary, practical- 

 ly all of the magnesia and lime are to be referred to the normal carbonate 

 forms. From the fact that a similar deficiency is found in all of the analyzed 

 carbonate rocks from the overlying Altyn, Siyeh, and Sheppard formations, it 

 is reasonable to suppose that it is not due to the necessary errors of analysis. 

 In all these cases the deficiency may be hypothetically explained by the presence 

 of small amounts of hydromagnesite, (MgC0 3 ) 3 Mg (OH) 2 + 3 H,0. The large 

 proportion of water expelled above 110° C. might also be referred in large part 

 to the basic carbonate. It is thus possible to conceive that 'from five to seven 

 per cent of the rock is made up of that substance. 



The specific gravities of three type specimens of the impure dolomite were 

 found to be respectively, 2-749, 2-777, and 2-782; the average is 2-769. These 

 values show that magnesia must be high in all three specimens. 



Though tbe dolomite occurs in massive plates from six to eight feet thick, 

 and though it is h?ghly homogeneous from top to bottom of the section at 

 Cameron Falls, yet a close inspection of the ledges shows that the rock is made 

 up of a vast number of thin, often paper-thin, beds. Scores or hundreds of 

 such laminae can be counted in a single hand-specimen of the massive dolo- 

 mite. Their surfaces are generally parallel, and cross-bedding, ripple-marks, 

 or other evidences of shallow-water deposition are absent. The character of the 

 rock, on the other hand, indicates that the carbonate was deposited quietly, 

 persistently, on a sea-floor not agitated by waves or strong currents nor receiv- 

 ing coarse detritus from the lands. The minute bedding and the exceeding 

 fineness of grain, point to an origin in chemical precipitation. The presence of 

 the carbonaceous dust suggests that the precipitation took place in the presence 

 ■of decaying animal matter and that the dolomite is thus analogous to the 

 chemically precipitated, powdery limestone now forming in the deeper parts 

 of the Black Sea. The theoretical questions regarding this and the other 

 carbonate rocks of the geosynclinal prism will be discussed in chapter XXIII. 



The Western Coal and Oil Company have made a boring a few hundred 

 yards from Cameron Falls and in the middle of the Oil creek anticline. The 

 log shows that the bore-hole penetrates 1,500 feet of hard limestones inter- 

 stratified with subordinate beds of quartzite and silicious argillite (metargillite). 

 All these rocks are fine-grained and, so far as one may judge from the drillings, 

 many are similar to common phases of the Waterton formation. The beds all 

 seem to underlie the visible Waterton dolomite conformably. We have, there- 

 fore, in addition to the exposed members of the Lewis series, at least 1,500 

 feet of still older beds which should be considered as belonging to the series. 

 TJntil these strata are actually studied at surface outcrops they cannot be 

 described adequately and for the present report, the Lewis series is considered 

 as extending downward only to the bottom bed of the Waterton formation 

 where it crops out at the cascade. 



At the depth of about 1,600 feet the bit of the boring machine passed from 

 the hard limestones into soft shales which persisted to the lower end of the bore- 

 hole about 2,000 feet from the surface. These shales are referred to ths 



