4l6 BULLETIN OF THE BUREAU OK FISHERIES. 



goitrous regions are located or the geologic formation from which the water supply 

 springs is the determining factor in the incidence of goiter. He has found regions 

 located upon and supplied with water from pure Jura formation, with from 12 to 40 

 per cent of goiter, and comes to the conclusion that the boundaries of locaUties in 

 which endemic goiter occurs are purely geographic, such as certain valleys, along cer- 

 tain rivers, or the sides of certain mountains. 



To determine whether there is any coimection between the geological formation at 

 the various hatcheries of the Government where trout are bred and theendemic conditions 

 existing in most of them, we have obtained from the United States Geological Survey a 

 statement concerning the formation at most of the centers of fish culture throughout 

 the country. All the data are included here, whether the station concerned is engaged 

 with trout culture or not. In some cases only general information is available. 



No correlation between geological formation and the occurrence of thyroid disease 

 is at present even suggested from the data at hand, which is here shown for purposes of 

 record in view of its possible future value. Most of the water supplying stations subject 

 to thyroid disease arises among the geological formations of primary order. Only one is 

 secondary (Triassic) and only a few tertiary and quaternary. 



ALASKA. 



Yes Baj'. — Crystalline schists, probably Carboniferous. 



ARKANSAS. 



Mammoth Springs. — Probably in Proctor or Potosi limestone. Cambrian system. 



CALIFORNIA. 



Baird. — Baird fi^rmation. Carboniferous system. This underlies a bluff of the Carboniferous 

 McCloud limestone. 



Battle Creek. — Tuscan tuff with some lava beds. Tertiary-. 



Mill Creek. — On border of alluvium of Sacramento \alley, and of Tuscan tuff and lava. Tertiary age. 



COLORADO. 



Leadville. — Crystalline rock, pre-Cambrian age. 



GEORGIA. 



BuUochville. — Formation not known. Probably granite and gneiss. Archean gneiss. 



ILLINOIS. 



Quincy. — Burlington and Keokuk limestones; Carboniferous age. 



Meredosia. — Glacial sand and clay. One hundred feet more or less below the surface is Carbonif- 

 erous limestone. Same as at Quincy. 



Manchester. — Devonian limestone with chert nodules. 



Fairport. — .\t contact of Carboniferous shales on Devonian limestone. 



