566 THE POPULAR SCIENCE MONTHLY 



(Fig. 2) located on an nnusnally low part of the bar, is said to have 

 collapsed bodily under the blow of one very large wave; while the 

 house shown in Fig. 5 was consumed more gradually after undermining 

 had allowed it to tip over. Indeed, the real damage was usually accom- 

 plished independently of direct impact upon the structures themselves. 

 Even where the beach was low and flat, as near the Octagon Hotel in 

 the town of Seabright, the foundations were sapped from under dwell- 

 ings, allowing them to tip over toward the sea; seldom if ever werei 

 these houses crushed in the first instance by the direct impact of the 

 waves. This is clearly shown in the case of the small houses of Fig. 3, 

 which were but a short distance from the hotel, and it is probable that 

 the hotel itself was first weakened by the undermining process. In 

 some cases the houses collapsed piecemeal as the sea advanced under 

 them ; or were crushed by the fall when they tipped over into the sea. 



Where houses were built on pilings driven into the beach sand the 

 removal of the sand left the buildings precariously supported on the 

 pilings alone until shaken down by the moderate waves of some later 

 storm. The successive stages of this process are well illustrated in Figs. 

 6-9, which represent four photographs of the same house. In Fig. 6 

 a small wave has passed through the outlying line of protecting piling 

 and is breaking against the bulkhead built to preserve the house from 

 destruction. Fig. 7 shows that the bulkhead has been breached and 

 that the corner of the house is beginning to be undermined. The 

 next figure represents a still later stage, when the sand has been re- 

 moved from under most of the house, leaving it supported by the pil- 

 ings alone. In this condition it fell an easy prey to the smaller waves 

 of later storms, and Fig. 9 shows the final wreck of the building. 



One reason for the destructiveness of the undermining action as 

 compared with the direct wave attack is to be found in the fact that 

 lines of piling and bulkheads were together able to break the force of 

 the waves to a large extent, but could not prevent the water of each 

 wave from washing against the foot of the low cliff, removing part of 

 the sand, and carrying it back to sea. In many places the lines of pil- 

 ing, and even the bulkheads, are still in a state of partial preservation, 

 while the cliff back of them is badly eroded and the superjacent houses 

 completely destroyed. The fact that the houses were at a higher level 

 than the cliffed beach was, of course, another factor which rendered 

 direct wave impact less destructive than undermining. 



Some have supposed that the active erosion of the New Jersey 

 coast by storm waves is the natural consequence of the gradual sub- 

 sidence of that coast which has been inferred by some geologists. The 

 evidence for and against the theory of subsidence has been considered 

 by the senior author in various publications, and need not be repeated 

 here. Suffice it to say that the loss of land during the recent storms 

 represents exceptionally rapid erosion of a purely temporary character, 



