1 873.] Colorado Gold Mines. 13 



nearly 1 per cent. Of the effect and importance of such an 

 error it is unnecessary to speak ; to all in the least acquainted 

 with analytical research there will appear full reason for the 

 more careful study of the subject.* 



These facts clearly show the necessity, — first, of great 

 care and great delicacy in* all manipulation connected with 

 experimental research; secondly, of carefully "weighing" 

 the individual merit of each result, and its relative merit in 

 the series of results. How this may be effected I have en- 

 deavoured to explain ; and I think that there would be no 

 series of observations (to which this or an analogous method 

 has not been applied) but would benefit by the application. 

 The application should of course proceed from the experi- 

 mentalist himself, but there are many series of results, the 

 members of which have been obtained by different processes, 

 that would be rendered still more practically useful by an 

 evaluation according to some one of the principles of the 

 theory of probabilities. Perhaps in future years the theory 

 may be universally understood, and it will not be required to 

 revert to the elements of the Science. 



II. GOLD-MINES AND MILLING OF GILPIN 

 COUNTY, COLORADO, UNITED STATES. 



By James Douglas, Quebec. 



OURTEEN years ago a party of miners detected gold 

 in Dry Creek and other spots near the present town 

 of Denver. The news spread ; a rush ensued, and 

 exploration was rapidly carried from the plains up the 

 gorges of the Rocky Mountains. Before 1859 had closed, 

 the gulches round Central City, 40 miles distant from Den- 

 ver, were swarming with gold-diggers ; and mining had also 

 commenced on the rich surface quartz of the lodes, whose 

 disintegrated debris had supplied the gold that enriched the 

 neighbouring valleys. 



In what is now Gilpin County, and within an area whose 

 centre is Central City, and radius about i|- miles, was dis- 

 covered, before 1863, a gold-bearing lode at almost every 

 hundred feet ; and many of these lodes were yielding gold 



* In the course of my experiments with the delicate apparatus employed in 

 this research, I have noticed some curious effeds of the adtion of heat upon 

 gravitating bodies. Led to pursue the investigation with specially constructed 

 apparatus, in air and in vacuo, I hope, at no distant date, to bring forward 

 some results. 



