fiS IOWA ACADF.MY OF SCIF.NCF.S. 



honor to reproduce these driivvinij-s in the Quarterly Jcnrnial 

 of the (Teoh)iric'-'il Society for May, 188!J, p. 188, in an arti- 

 cle: "On the Growtli of ( ■rystals in liifueous Rocks after 

 Consolidation." In this interestinof paj^er Prof. Judd con- 

 cludes that the crystal enlarg-ements from Missouri belong- ti> 

 the same sfeneral class observed in frairniental rocks ])V dif- 

 ferent workers, especially by Irving- and Van Hise.3 



It seems to the writer that the examples produced l>y Prof. 

 Judd from Mull, in the Western Isles of Scotland, Jire so dis- 

 similar to the Missouri specimens that it is unsafe to class 

 them together. His is a Lahradorite-cuidesite with large por- 

 phyritic crystals of labradorite, and a g-lassy base. The Mis- 

 souri specimens are from a fairly well crystallized granite: 

 on(^ having- idiomorphic crystals, it is tru(>, but which is very 

 far removed from a rock with a glassy base. Judd's idea is 

 that "the g-rowth of crystals of felspar and quartz goes on, 

 at the expense of a more or less vitreous matrix, long after 

 the solidification of the rock," etc. 



Neither the field work nor the laboratory work on the Mis- 

 souri crystalline rocks is completed. The writer will hold 

 himself ready to alter his views on any of the subjects, or 

 to entirely abandon them, should subsequent evidence demand 

 it. 



THE NATIVE FOOD FISHES OF IO\A/^A. 



RY PROF. SKTH K. MEKK, \I. S- 



iAtstract.) 



In the waters of Iowa, including- the Mississippi River 

 along her eastern border, are found about one hundred spe- 

 cies of fishes, of these about thirty-six are usually found in 

 our markets, and are regarded as food fishes of more or less 

 value. About eight of the remaining species are large enough 

 for food, but for various and just reasons, have no market 



See Bull. 8, U. S. G. S. and Am. J. Science, (3). 30. 233, 35. 



