72 G. F. Kunz — Mineralogical Notes. 



affirm, in relation to a given epoch, that because he could not 

 find the remains of plant and animal life which he considered 

 could have existed under glacial conditions, no glacial condi- 

 tions existed during that epoch. And the more so seeing how 

 difficult it is to determine with certainty, more especially in 

 relation to remote periods, how much cold a plant or an ani- 

 mal might be able to endure. 



Besides all this, supposing the organic remains of former 

 glacial epochs were found in abundance, these remains would 

 probably mislead most geologists. For if the theory of the 

 glacial epoch, advocated in " Climate and Time" be correct, 

 viz : that those epochs consisted of alternate cold and warm 

 periods, it is evident that the greater part, or nearly all of 

 those remains would belong to the warm or interglacial peri- 

 ods. A geologist who did not believe in interglacial periods, 

 judging from the character of those remains, would naturally 

 come to the conclusion that the epochs in question were warm 

 and equable, not glacial. His disbelief in interglacial jDeriods 

 would thus induce him to give a wrong interpretation of the 

 facts. 



Assuming that a glacial epoch occurred at every time that 

 the earth's orbit attained a very high state of eccentricity, it is 

 quite apparent, when we reflect on the imperfection of geolog- 

 ical records on the matter, that we have in reality about all 

 the evidence which we could possibly expect of the existence 

 of such epochs. 



Art. IX. — Mineralogical Notes, on Fluorite, Opal, Amber 

 and Diamond • by George F. Kunz. 



Fluoi'ite. — About four years ago, a small vein of fluorite in 

 Archsean limestone was discovered in the town of Macomb, 

 St. Lawrence Co., New York. It was worked from time to 

 time until last summer, when the vein suddenly widened, 

 breaking through into a cavity or cave. This cave is 22 feet 

 north and south, and 18 feet east and west, and is 8 feet below 

 the surface. It dips from the south to the north, and is about 

 8 feet lower than at the mouth or entrance. It is about 5 feet 

 between the walls. A pool of water in the northeast corner, 

 about two feet in depth, often rises ten or twelve inches dur- 

 ing the day. The top, bottom, and sides were lined with a 

 magnificent sheet of crystals, varying from one to six inches in 

 diameter, each in turn forming part of larger composite crys- 

 tals. Between the floor and the walls was a layer of partly de- 

 composed calcite, which was readily removed, so that groups 



