76 THE liUILDING OF AN ISLAND. 



same appearance as the rock of Virgin Gorda, and has, also, a sj)heroidal 

 structure. In the eastern part of the island some stratified white rocks seem 

 to occur, hut liaving seen them only from the sea, at a considerable distance, I 

 cannot give any description of them." From our present standpoint it would 

 be very interesting to know something about those " stratified white rocks." 



Turning to our sister island of St. Thomas, 40 miles away from us to the 

 north, we find no "stratified white rocks" there to help us. St. Thomas has 

 the older set of our Santa Cruz rocks, but the younger set (the limestones) are 

 entirely wanting. Possibly they were lodged there on the top of the older 

 rocks, but have been since washed away, as perhaps they were, from the tops 

 of the northern and eastern hills of St. Croix. However that may be, it is 

 certain that the limestone system of St. Croix is entirely wanting in St. 

 Thomas, and consequently we lose the geological evidence as to the direction 

 of the later tipheaving force. About the direction of the more ancient upheaval 

 we have, however, very good evidence, and it is extremely interesting to find 

 that the ancient rocks have been thrust up in ridges or waves, lying parallel to 

 the like waves in St. Croix ; in other words, the St. Thomas rocks have been 

 subjected to the same thrusts as have acted on the similar ancient rocks of St. 

 Croix. For evidence of this we have the quarries and other rock exposures 

 in and about the town. In a quarry on the west side of the " Field" we find 

 plainly stratified rocks of the indurated clay type, much like those we see near 

 Christiansted, and we find that they dip at a high angle (about 40 degrees) to 

 about northeast. Across the " Field," on its eastern side, we find another 

 quarry showing hard blue-beach conglomerate. Most of the embedded frag- 

 ments are somewhat rounded, as though water-worn, and the mass is so thick 

 that we at first discover no stratification, but after a careful search, we find in 

 the northwest corner of the quarrv some fine-grained blue-beach without 

 embedded pebbles, and showing ribbon-like markings indicating stratification, 

 the layers dipping in the same direction as those of the first-named quarry. 

 When we ascend the hill towards Louisenhoi and Ma Folic, we see similar 

 indications of the original stratification of the rocks and of the dip being to 

 about northeast. But when, starting from our first named quarry, we move 

 southwards towards the town, we soon meet (near the Epidemic Hospital) 

 with similar indurated cla)^ rocks distinctly stratified, but dipping, not to north- 

 east, but to so2ith or south-by-east. If we ascend the road up the hill to the 

 west we shall find further evidence of this southerly dip, and we shall meet 

 with it here and there in various parts of the town. Hence we have dis- 

 covered that the town stands on the south slope of a wave of the old rocks, 

 which, immediately behind it towards the north, has been cut down into a 

 slight depression, while the northern slope of the wave appears just beyond 

 and in the higher hillsides. 



This wave in the strata is of especial interest, because it appears, in the 

 hardness of one of its beds, to be the cause of the peculiar hill spurs which 

 have given the opportunity of building a considerable part of the town on 



