386 Winchett — Geological Age of the Saganaga Syenite. 



T =286°, which was about the absolute temperature at Moun- 

 tain Camp, and £=3'53, as previously determined, we get 

 I = 1*185 I, that is, by the formula, the intensities at Moun- 

 tain Camp should be increased over those made at Lone Pine 

 at a higher temperature and then reduced for difference of 

 level to Mountain Camp, in the ratio of 1 : 1"185. But we 

 have seen that the bolometer observations make this in the 

 ratio of 789 : 1284 or 1 : l - 63. Observations, therefore, indicate 

 that in the case of both the registering actinometer and the 

 bolometer, a reduction for difference of temperature is required, 

 but what is perplexing in the matter is, that the reduction 

 required, especially in the case of the bolometer, is much 

 greater than that given by the preceding formulae of reduction. 



It is not to be understood that this is a matter which affects 

 any of Langley's results, for he used the bolometer to deter- 

 mine the relative intensities only of the several different wave- 

 lengths, which were all made at the same times for each series, 

 and consequently at the same temperatures. 



In what precedes, the writer wishes to state in conclusion, 

 that he has ventured with considerable timidity upon unfa- 

 miliar ground, and that it is possible he may have made some 

 blunders. If so, it will be matter for discussion and correction. 



Martmsbiirg, W. Va., Jan. 7. 



Aet. XLIII. — Geological Age of the Saganaga Syenite / by 

 Horace T. Winchell, F.G.S.A. 



The Saganaga Syenite is an area of syenitic and granitic 

 rocks occupying largely the shores and islands of the lake 

 called by the Ojibways Kasaganaga (the lake with many 

 islands or the lake surrounded by thick forests, as differently 

 interpreted ), which lake is situated on the international bound- 

 ary line between Minnesota and Ontario, and has many long 

 arms extending north and south from the line. This syenite 

 is also found around Sea Gull lake, and occupies an area of 

 about 100 square miles in the State of Minnesota, in townships 

 65 and 6% north, ranges 4 and 5 west of the fourth principal 

 meridian. The hills surrounding these lakes rise to a height 

 varying from 100 to 300 feet, and consist of bare glaciated 

 knobs of syenite. These hills are apparently the northeastern 

 prolongation of the Giants' Range, a mountainous range of 

 syenitic rock extending in a general northeast direction from 

 the Mississippi River to the Canadian boundary line. 



The general composition and structure of the syenite have 

 been fully described in the Sixteenth Annual Report of the 



