222 



BULLETIN OF THE BUREAU OF FISHERIES 



the relation of the amount of fouling to the amount of time spent at sea. It will be 

 seen easily that this relationship is constant and that the proportions appear to 

 vary inversely as the percentage of time spent cruising. 



In Table 4 is shown a classified list of the various types of ships, indicating the 

 number in each group, with their respective amounts of fouling in relation to the 

 length of the last dry-docking period. Of the ships that docked within three 

 months after a previous dry docking it will be seen that in all groups, excepting the 

 battle cruisers, the majority of the ships were clean or only lightly fouled (for those 

 docking), while in the next three months (i. e., from three to six months after 

 previous dry docking) the majority were found to be in the classes of lightly or 

 moderately fouled ships. It is also of interest to note that in columns 6 and 7, the 

 periods longer than 18 months, the preponderance of heavily fouled vessels is very 

 conspicuous, especially in the case of vessels "out of commission." 



From these tables it is seen easily that the time between dry-docking periods is 

 of great significance, but the use made of this time, either in cruising or in port, 

 is of even greater importance. It can be seen, in addition, that the amount of 

 fouling increases with the length of time that elapses since the previous dry docking 

 (fig. 26) but becomes proportionately less with any increase in the percentage of 

 time spent cruising. (Fig. 28.) 



Table 4. — Analysis of the difference in docking periods for diverse types of ships and the relative 

 amount of fouling on these ships, grouped according to length of time elapsed since previous dry 

 docking 



[H heavily fouled; M, moderately fouled; L, lightly fouled; N, no fouling; X, aberrant cases, due to putrid waters of the Phila- 

 ' delphia Navy Yard] 





Class 



of vessel 



lto3 

 months 



3 to 6 

 months 



6 to 9 

 months 



9 to 12 

 months 



12 to 18 

 months 



18 to 24 

 months 



24 months 



Colliers an 



d miscel 









1H 



4H 





1 H 









2M 



4M 



1 M 



2 M 













2 L 



3 L__ 



1 L 

























1 H 







2H 













3 M 



1 M 











1L 





2 L 

















2H 







1H 













1 M 



3 M 







2 L... 



3 L 



4 L - 



2 L 



2 L 







1 N 



1 N 

























Passenger 







1 L 





5 L 



1 L 



















3 N 























Freighters 









5H 



1H 











6H. 

 2 LX. 





1 M 



2 L 



10 M 



15 L 



3 M 



14 L 



3 M 



4 L 



1 L 







2N 



6N 



2N 

















3H 









Out of commission 





3 M - 



2 M 



2M 



1 L 



























3H 



3 H 



3H 











3 M 



2M 



3 M 



1 L 



1 L 





1 L 



1 T, 



1 LX 





1 N - 

















1 H 



3H 















1 M 



1 M 











2 L 























