TWENHOFEL: EXPEDITION TO THE BALTIC PROVINCES. 353 



coral masses. Some of them may also have been subsequently formed 

 by the settling of the sediment over the coral ridges, which would 

 remain rigid while that filling the basins on each side would settle. 

 At any rate, few or none of these inclinations and vmdulations have 

 any significance in connection with the stratigraphic relations. 



Among coral reefs the strata in the different channels are more or 

 less isolated, and they would dip away from the reefs in a way that 

 would appear to carry them far below other strata in the direction of 

 inclination, and if this basin or synclinal-like structure could not be 

 discerned the conditions would lead to divergent interpretations. 

 I do not wish to argue that younger strata are not present in the south- 

 eastern part of the island, nor that strata of the same age occur over 

 all parts of the island. I believe the truth lies between the two 

 extremes, but wish to emphasize the fact that in each of the channels 

 between the reefs there will be apt to be a different lithology, a differ- 

 ent structure, and a different fauna from that in any other channel. 

 Since the rate of deposition in each channel will be different from that 

 in another, it follows that strata of a certain time interval will lie in 

 one channel at a higher or lower level than that of another channel, 

 and each will be below the rock of the reef which represents the same 

 time interval. 



That to a considerable degree, the conditions described represent 

 those obtaining in the Gotland section I feel assured. These views 

 open a most interesting field for investigation, which should be begun 

 by a careful mapping of every coral reef which can be discovered on 

 Gotland, and this should be followed by a careful study of the inclina- 

 tions of the strata, and these should also be mapped in order to see 

 the relation of these inclinations to the coral reefs. Then the deposits 

 and fauna of each basin between the reefs should be studied in an 

 endeavor to correlate the strata of the different basins. When this is 

 done the controversy as to whether certain strata on one side of the 

 island lie underneath or above certain strata on the other side will have 

 disappeared, and data will have been collected upon which something 

 besides hypothesis can be erected. The detailed work that Drs. 

 Munthe and Hedstrom are doing is laying the foundation to the ulti- 

 mate untieing of this Gordian knot of Baltic stratigraphy. 



