1918] Davis: The Radiolarian Cherts of the Franciscan Group 403 



of the chert in lenses. There appears no reason why submarine 

 siliceous springs should not exist. Where known on the land, such 

 springs are associated with vulcanism, and it is probable that sub- 

 marine siliceous springs would be related in some way to igneous 

 activity beneath the sea floor. 



Submarine springs are known, though, from the nature of the 

 case, one would expect records of them to be scarce. 



Russell 168 describes a number of sublacustral springs in Mono 

 Lake and refers to sublacustral springs elsewhere. In Mono Lake, 

 the upward flow of water discharged from some of the springs causes 

 a low moundlike elevation of the surface of the lake. The flow of 

 discharged water is sufficient to deflect a boat. 



There is a large submarine spring off the coast of Florida, about 

 nine miles south of St. Augustine and about two miles from shore. 

 The orifice is about sixty feet across and the water emerges with 

 enough force to cause a distinct convexity of the surface in calm 

 weather. It is difficult to row a small boat across it on account of the 

 outward movement of the water. 169 This spring is shown on the 

 U. S. Coast and Geodetic Survey Chart — St. Augustine Inlet to Hali- 

 fax River, Florida. The general depth of water is fifty-five feet, but 

 in the spring a sounding of 126 feet was obtained. 



At Tarpon Springs, Florida, a spring emerges beneath the waters 

 of a small shallow bay, a few feet below mean tide level. A sounding 

 of 125 feet was obtained in this spring. 



According to E. Lester Jones, superintendent of the U. S. Coast 

 and Geodetic Survey, these springs were merely noted incidentally, 

 and it is probable that a systematic investigation would reveal many 

 others. 170 



All during the Franciscan period there appear to have been irrup- 

 tions of pillow lavas. This is shown by the finding of boulders of 

 basic igneous rock of Franciscan type and boulders of glaucophane 

 schist in conglomerates in the Franciscan sandstone. In California, 

 glaucophane schists are known only in the Franciscan and appear to 

 be always the result of contact action of basic igneous rocks. 



In working in areas of Franciscan rocks one is so impressed by 

 the frequency of intrusive contacts of the pillow basalt, that he . is 

 likely to regard all these rocks as intrusive masses which came into the 



"a U. 8. Geol. Surv. 8th Ann. Rept., pt. I, p. 287, 1886-87. 



"a Watson and Sanford, U. S. Geol. Surv., Water Supply Paper 319, p. 208, 

 1913. 



I'o Personal communication. 



