FOULING OF SHIPS' BOTTOMS 203 



EXTENT OF FOULING 



The prevalence and amount of fouling is surprising to anyone who witnesses 

 for the first time the docking of mariae vessels. In earlier times it was not uncom- 

 mon for ships to have their entire bottoms incrusted with organisms to a depth vary- 

 ing from 5 to 9 inches, with estimated weights of 300 tons or more. In recent years, 

 due especially to more regular and frequent dry dockuig, such conditions are experi- 

 enced but rarely; but even to-day, after vessels have been at sea for 6 or 8 months, 

 they frequently accumulate growths from 2 to 3 inches in depth, and vessels with 

 from 50 to 100 tons of fouling are seen frequently. When one realizes that all ships 

 become foul if submitted to the usual environment, the extent and prevalence of 

 fouling can be realized. In Figures 11, 12, and 13 are shown conditions typical of 

 lightly, moderately, and heavily fouled ships, while in Figures 14 to 19 are seen the 

 kinds of growths contributing to these conditions. 



In Table 1 is given a list of all of the vessels examined during this investigation, 

 with notations regardiag the amount of fouling on each. By reference to this table 

 it can be seen that there is great variation in the amount of fouling on various ships. 

 The reasons for this will be discussed under separate headings in another section of 

 this paper dealing with the factors that determine fouling. 



