112 C. P. Williams and J. F. Blandy, 



the ether examined with tbe microscope for small prismatic crys- 

 tals; if a few drops of sulphuiic acid diluted with its volume of 

 water are added in the cold and there are alkaloids present, they 

 will dissolve, only so much picrotoxine passing into solution as 

 is due to the water present, about one part for one hundred and 

 fifty of water. A few drops of an alkaline _ fluid will dissolve 

 the crvstals and on applying heat the fluid will become first yel- 

 low and when more strongly heated will become brick-red, A 

 small portion ground in a watch-glass with nitrate of potassa and 

 sulphuric acid gives a solution which when rendered alkaline by 

 potash or soda becomes a bright-red. 



University of Michigan, Ann Arbor, March 26th, 1862. 



Aet. XIV. — Smne contrihutioyis to a knowledge of the constitution of 

 the Copper Range of Lake Superior; by C. P. WILLIAMS, A.M. 

 and J. F. Blandy, M. and C.E. 



The enterprise and vigor with which the exploitations of tlie 

 Portage Lake District of the Copper region of Lake Superior 

 have been carried on within the last few years, have developed 

 many facts of great interest and importance in the constitution 

 and structure of the Trap range of that place, beyond what have 

 been made public through the medium of the excellent worK, 

 ''The Metallic Wealth of the U. S./' by J. D. Whitney, Esq., | 

 and the reports of the geologists having in charge the examina- . 

 tions of the Lake Superior mineral districts. I 



The Trap range at Portage Lake has a width, as far as known, [ 

 of about three miles, and is made up of a series of compact, gran- | 

 ular, amygdaloidal traps, with occasional intercalations of sand- 

 stones and conglomerates, the whole having a strike of N. 32 ^■ 

 and S. 32° W., with a dip of from 16° to 75° N.W.— the highest 

 angle of dip being near the southeastern boundary of the rauge. 

 while towards the northwestern limit, the rocks become more 

 and more horizontal, until, finally, the sandstone which succeea^ 

 it becomes absolutely so. 



Coincident, both in course and dip, with the rocks of the range 

 are the so-called lodes of the district, which present no tcai;:^'- 

 of fissure veins, but are simply beds of highly amygdaloid;^- 

 carrying throughout their whole width— from 6 to 40 feet 

 masses and grains of native copper, with a small amount 

 tive silver, the cavities of the rock being large and fillea 

 calcareous spar, quartz, chlorite, and several minerals of li^c — 

 lite family. t 



Several of the intercalated beds of sandstone and conglomerate i 

 also contain minute particles of copper, but none of these as ye | 



