MUSEUM OF COMPARATIVE ZOOLOGY. 17 



taincd a large amount of metal, it would be the first to be precipitated 

 to the bottom of the water into whicli the lava was vented. The lava 

 would not run in a solid stream from the crater, and solidify as a stratum 

 in the water, but the moment it touched the adverse element it would 

 be shivered to atoms, and thrown back into the atmosphere with the 

 steam it would create, and the lighter portions would naturally arise in 

 dust and ashes, and be carried by winds and waves and tides to remote 

 localities, while the heavier materials would be precipitated in the 



vicinity in the order of their density We may refer most of our 



great Azoic beds of magnetic and specular ores and red oxides of iron to 

 this cause, and their formation to these agencies. We may also refer 

 the alluvial or drift gold in the ' placers ' of California and the ' diggings ' 

 of Australia to the same causes." {I, c, p. 533.) 



It is such theories as this, and many others touched upon in this 

 paper, that give the "funny side " to our work, and serve to enliven 

 the tedium of it; otherwise they would not be worthy of preservation. 

 They stand as the caricatures of science, although they were evidently 

 sober realities to their authors. 



A series of papers was published by Dr. Hermann Credner in 1868- 

 70, the titles of which will be given in the literature at the end of this 

 work. He divides the formations as follows : the gneiss-granite, or 

 Laurentian formation, and the limestone-quartzite-iron-stone, or Huro- 

 nian formation. The latter is said to unconformably ovei-lie the former, 

 but the evidence, so far as given, is derived from the dip and strike of 

 the .lamination, and not from observation of the kind and manner of 

 their contact. The diorites, iron ores, and all their associated rocks, 

 except a few, are regarded as interbedded formations. The iron ore is 

 supposed to have all originally been magnetite, and in part changed 

 since to hematite and limonite. Near Marquette certain diorites were 

 seen by him to be eruptive ; therefore they were taken to be of differ- 

 ent age from the interbedded diorites associated with the iron ore, and 

 younger than the Huron ian. 



In Prof. A. Winchell's Report of Progress of the Geological Survey 

 for 1870 we find the following remark : "The rich masses of magnetic 

 and hematitic ores of iron are found not to be those erupted outbursts 

 which the older geologists were inclined to regard them. They are 

 simply constituents of the system of sedimentary deposits which make 

 up the Huronian System of Michigan. The diorites of the region appear 

 to be equally of sedimentary origin, and are found strictly interstratified 

 with chloritic, siliceous, talcose, argillaceous, micaceous, and hematitic 



VUL. VII. — NO. 1. % 



