142 BULLETIN OF THE 



ciently powerful to break up and pack large shells in the manner 

 acconiplished by swift moving waters. It is possible that in part the 

 growth of the Cincinnati anticlinal took place at a later date, but the 

 greater part of its elevation was probably due to Silurian time. It 

 seems to me that it can best be explained in the manner above indi- 

 cated. It is a noticeable fact, that the Cincinnati'axis is most developed 

 along the line to the east of which this accumulation in the paleeozoic 

 seas derived from the bordering land was most extensive. Moreover, 

 the general form of the elevation is quite comparable to that of Florida, 

 though the axis of position is widely contrasted in the two cases. 



If I am right in my supposition as to the oi'igiu of these curious 

 reliefs in the region about the Gulf of Mexico, if the anciently developed 

 axis of the Mississippi valley, the Floridian peninsula and that of Yuca- 

 tan, and the greater islands of the Caribbean, represent the results of 

 Cdunter-thrust arising from the imposition of sediments on the sea-floor, 

 it is evident that we have iii this part of tlie earth's sui'face a remark- 

 able exemplification of the effect of weight on the attitude of the crust. 

 It must be confessed that the matter is extremely speculative. I should 

 hesitate to give it note, were it not for the fact that the whole problem 

 as to the effect of weight of sediments is now much under discussion, 

 and it appears to me worth while to call attention to this district, where 

 there may be sometliing like critical evidence as to the verity of the 

 hypothesis. 



The detailed topography of Florida is interesting from the light it 

 throws on two important jn'oblems, the growth of coral reefs, and recent 

 changes in the path of the Gulf Stream. As to the first of these ques- 

 tions I have little to add to the considerations which have been brought 

 forward by other writers. This little pertains to the distribution of the 

 livinir and the elevated reefs on the eastern shore between the southern 

 part of Key Biscaync and St. Augustine. Inside the living reef between 

 Key West and the southern part of Biscayne Bay the southern coast of 

 Florida is low. From the reports of others it appears likely that thei-e 

 are ridges, probably in their nature coral reefs, such as Long Key, at a 

 distance of a score or more miles from the swampy border of the land. 

 Xear the southern end of Biscayne Bay we find the first distinct reef 

 near the shore. This reef comes above tlie level of the sea about ten 

 miles north of Mangrove Point, just to the west of Old Rhodes Key. 

 It gradually rises, until at Cocoanut Grove, immediately west of Key 

 Biscayne, it has a heiglit of about twenty-two feet and a widtli of about 

 two miles. As the upitermost part of the deposit consists of character- 



