1900] ENTOMOLOGICAL SOCIETY. 23 



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A little further north we came upon two outcrops of limestone each about seventy 

 feet in length ; one runs parallel with the river and the other at right angles. On each 

 side of these outcrops kettles are ranged. These vary in size and shape. They are from 

 one-half to two thirds of complete globes. Crevices in the limestone are filled with 

 material of the same composition as the concretions. Though we searched diligently for 

 impressions of calamites we did not succeed in finding any at this place. 



At a place three miles up the Sydenham from Shetland the Limbton limestones are 

 exposed. They are very fossiliferous and are crowded with Spirifera Mucroaata. 



The Rev. Joa. Philp also visited the Enniskilleu gum beds and reported to us his 

 findings, and sent a fine specimen of what he terms mineral Caoutchouc. It was ob- 

 tained from lot 16, second con., Enniskillen, near Oil Springs. 



The bed is situated on the surface, and is quite extensive, though much of it has 

 been removed and used as fuel for steam raising. With a fan blast it burns well. In 

 appearance it resembles tar. It is almost jet black, dense and solid, somewhat resembling 

 asphalt. People select the cleaner parts and use it as chewing gum. They say it is 

 better than it looks. It is probably of the same origin as the petroleum found in the 

 same vicinity. 



Mr. Philp also examined the bituminous shales of Alvinston which are exposed at 

 that point for nearly a mile along the river. They belong to the Portage Chemung 

 group. He found one impression of a Calamite, very distinct. The stratification and 

 the cleavage are noteworthy and the nodules of iron pyrites are very beautiful. At 

 this point there is no trace of a kettle. He thinks the kettles are found only in the 

 lowest portion of this formation. At least that is the case at Shetland, where the older 

 strata are exposed. 



The Lake Superior Copper Mines. 



Mr. Groodburne, who visited the Lake Superior copper mines in October, 1899, read 

 a paper descriptive of that region, opening with a brief descripiion of copper and its ores. 

 The first record of the discovery of copper in the Keeweenaw Peninsula, Michigan, was 

 in 1636, and from that date its history was traced down to the present day. Mining, 

 however, dates only from 1831, when Dr. Douglass Houghton, while a member of the 

 Schoolcraft expedition, first made known the great wealth of the peninsula, and in 1834, 

 the government first opened up the country to mining. From a review of the history of 

 early mining, Mr. Goodburne proceeded to a description of the principal mines, chief 

 interest centering in the great Calumet and Hecla, which yields 100,000,000 pounds of 

 refined copper annually from the conglomerate lode underlying 20 acres of surface, a 

 product valued at $18,OCO,000, taken from under land, which originally cost $1.25 per 

 acre, or $25.00 for the most valuable copper mine in the world. 



Tho' great Keeweenawan formation consists of a series of eruptive beds, alternating 

 in the upper division with sandstone and conglomerates, the whole lying above the 

 Huronian slates, schists and metamorphic rocks. The formation was, probably, originally 

 horizontal at the bottom of the ancient sea. The system to the east is the Medina divi- 

 sion of the Silurian formation, a time when great volcanic forces disturbed the earth ; but 

 it was probably the subsequent movements of the crust which tilted the beds so as to 

 form a great trough or synclinal. The eastern edge is on the end of Keeweenaw Point, 

 and the western across the Minnesota border. Michipicoten It-land and the Nepigon dis- 

 trict are on the reverse, or northern, fold of the synclinal, for while the Michigan edge 

 dips toward the northwest, the northern edge dips in the opposite direction, but it i«? 

 very much broken by depressions, and not so easily traced as the southern edge. The 

 lower beds of the Keeweenawan formation consist mainly of a series of coarse crystalline 

 gabbros, from 20 to 50 feet thick. There are 4,000 or 5,000 feet of these lava flows, after 

 which the eruptions became somewhat different in chemical character, and more frequent, 

 with thinner flows. These flows contain the copper. The lava is generally basic, like 

 basalt, but acid and intermediate types are present. Among the typical hinds may be 

 mentioned gabbro, diabase and melaphyr. including tho amygdaloidal examples of the two 

 latter, in which is the copper. Other rocks are the acid lavas, including felsites and 

 porphyries, which have furnibhed much of the detritus for the sandstones and conglomer- 

 ates, and these acid lavas, which do not flow as far or so freely as the basic, quite often 

 trend across the other rocks in the form of dikes or bosses, with dome-like summits. 



