242 



BULLETIN OF THE BUREAU OF FISHERIES 



A similar series of panels was exposed in the following summer (1923) at Woods 

 Hole, Mass. (fig. 35), with, the results shown in Table 9 in which is shown their relative 

 efficiency on the basis of the area free from fouling. All films were in excellent 

 condition. No corrosion was evident anywhere. Fouling was caused largely by 

 Bugula, with some Alga and a small amount of Obelia. Although no barnacles 

 attached during this period of the year, the same relative differences in amount 

 of fouling are seen here as in the plates at Beaufort. 



Table 9. — Results of plates exposed at Woods Hole, Mass., submerged on May 81, examined July 25, 

 1923, painted with two coats each of the "photographic" color paints, as prepared by Henry A. 

 Gardner 



No, 



Plate color 



Film 



Fouling 



Percentage 

 of surface 

 not fouled 



Black 



Dark green.. 



Red.... 



Chocolate... 



Yellow 



White 



Light green. 

 White 



Good... 

 .do. 

 .do. 



.do. 

 .do. 

 .do. 

 -do_ 

 .do. 



Heavy... 



do.... 



do.... 



do.... 



Medium. 



do.... 



do.... 



Slight.... 



10 

 20 

 20 

 20 

 30 

 50 

 60 

 90 



It was soon realized, however, that these results were open to various explana- 

 tions, for the material employed to produce a given color was different in each case, 

 and this factor alone might account for the differences in fouling. Accordingly, 

 other methods of attack on this question were planned. These included, first, a 

 submerged electric light with colored panels on each side; second, a set of colored 

 tiles; and, third, a series of experiments in which the active cyprid larvse were 

 exposed in the laboratory to light of known wave length and intensity. 



SUBMERGED COLORED TILES 



Woods Hole, Mass. — During the summer of 1923 a series of colored tiles, with 

 both glazed and unglazed surfaces, were submerged by the author at the biological 

 station of the United States Bureau of Fisheries at Woods Hole, Mass. Tiles were 

 used in these experiments to eliminate all possible effects of any toxic action that 

 might have resulted from the use of pigments needed as coloring matter in the 

 paints employed in the previous experiments with panels. These tiles were sub- 

 merged in two sets of panels — eight glazed in one panel and five unglazed in the 

 other. The regulation size was 6 by 6 inches, but a few were half size, measuring 

 3 by 6 inches, and about one-half inch in thickness. 



These tiles were submerged on May 13, 1923, and were examined from time 

 to time until July 25. The amount of fouling was noticeably less on the lighter- 

 colored plates. However, there were several apparent inconsistencies, the glazed, 

 black tile having less fouling than any of the others, excepting the two white tiles, 

 whereas the unglazed, black tile was the most heavily fouled. However, the follow- 

 ing gradation, from least to most, was noticeable in amount of fouling: 



(a) Glazed set: White, black, light green, yellow, pink, blue, green, red, and 

 dark green. 



(6) Unglazed set: White, yellow, red, dark green, and black. 



