REPORT OF TEE CHIEF ASTRONOMER 3 



SESSIONAL PAPER No. 25a 



studied and determined by Drs. T. W. Stanton, G. H. Girty, and C. D. Walcoti 

 of the United States Geological Survey, and by Dr. H. M. Ami, of the Geological 

 Survey of Canada. Professor M. Dittrich, of Heidelberg, Germany, and Mr. 

 M. F. Connor, of the Canadian Department of Mines, performed valued service 

 in making the large number of chemical analyses noted in the report. The 

 draughting has been performed with zeal and care by Mr. Louis Gauthier, of 

 the Chief Astronomer's office at Ottawa, and by C. O. Senecal and his assistants 

 of the Geological Survey. A number of professional geologists have discussed 

 theoretical matters and thus markedly assisted in the composition of the report. 

 To each of these gentlemen the writer tenders his thanks for all their kind and 

 efficient help. Equally sincere thanks are due to the president and corporation 

 of the Massachusetts Institute of Technology, who for more than two years have 

 granted every available facility for the preparation of this report. 



Special mention at this place may also be made of the fact that chapter 

 XIV is largely a direct quotation from Mr. R. W. Brock's report on the 

 Geology of the Boundary Creek Mining District.:}: The corresponding part of 

 sheet ]STo. 10 has been compiled from the map accompanying Mr. Brock's report. 

 In view of the care spent on this part of the Boundary belt by this able investi- 

 gator, it seemed inadvisable to spend much of the limited time allotted to the 

 transmontane section on the Boundary Creek district. Accordingly, the present 

 writer made no more than a couple of rapid east-west traverses across the 

 district, corroborating, so far, the accuracy of Mr. Brock's mapping in a par- 

 ticularly difficult terrane. 



Professor Penhallow's paper on the collection of fossil plants forms an 

 appendix to the present report. 



Collections. — During the survey 1,525 numbered specimens, with many 

 duplicates, were collected. Each of the localities, whence the specimens chemi- 

 cally analysed were taken, is noted on the map sheets with a small cross and 

 the collection number. Some 960 thin sections of the rocks were prepared and 

 studied. Sixty rock analyses and one feldspar analysis were made for the report. 

 Thirteen hundred photographs were taken by the writer, besides which many 

 hundreds of others were taken by the photo-topographic parties operating for 

 the Canadian branch of the Boundary Commission. 



Previous Publications by the writer on the Forty-ninth Parallel Gevlogy. — 

 After each field season a brief account of the ground covered was published either 

 in the summary report of the Director of the Geological Survey of Canada or , 

 in the annual report of the Chief Astronomer of Canada. As the work pro- 

 gressed it was thought advisable to publish separate papers on certain general 

 and theoretical problems, which had arisen during the survey of the Boundary 

 belt. The list of these papers, some of which, in more or less amplified form, 

 form parts of this report, is as follows : — 



JR. W. Brock, Annual Report, Geological Survey of Canada, Vol. 15, 1902-3, Part 

 A, pp. 98 to 105. 



25a— Vol. ii— lj 



