Two experimental asse-nblies vrere constructerl, the first for hot water 

 studies consists of three water lines sunplyin^^r continuouslj'- flomng 

 sea water to individual vreir boxes. One of the lines furnishes normal 

 sea water as a control and provision is made to raise the temperature 

 of the water in the other two lines to a selected point on any time 

 schedule desired. The samples under investigation are placed in the 

 weir boxes durinc;; the test runs. 



The second assembly consists of ei^ht lines supplyiniq; identical weir 

 boxes with water which may individually be chlorinated to selected re- 

 sidual concentrations of chlorine by ei.crht automatic feeders on prede- 

 termined schedules. Provision has also been made to introduce tempera- 

 ture changes as well as chlorination. 



During the summer of 19^0 the effect of rather broad residuals of chlo- 

 rine on the teredine borers was studied. Future reference to chlorine 

 concentrations in these remarks will refer to residuals. 



The follomng concentrations were established in the eight weir boxes, 

 the test pieces being 2"x[t"xU" wooden blocks: 



1. Conti'ol 



2. Continuous chlorination at 0.2^ ppm 



3. Continuous chlorination at 0,^0 ppm 



h. Intermittent chlorination at 1.^ ppm, 2 hours on, h hours off. 



5. Intermittent chlorination at 3.0 ppm, 2 hours on, h hours off. 



6. Intermittent chlorination at 1.5 ppm, 2 hours on, 2 hours off. 



7. Intermittent chlorination at 3.0 ppm, 2 hours on, ,2 hours off. 



8. Intermittent chlorination at 0.5 ppm, 2 weeks on, 2 weeks off. 



This series commenced on July 3lGt and was terminated on September 29th 

 with the results of the final inspection of the blocks as follows: 



#1 - Control, 200± Teredinidae 



/'2 - Continuous .25 ppm - no borers. 



//3 - Continuous .$0 ppm - no borers. 



i^h - Intermittent 1.5 ppm, 2 hrs. on, h hrs. off - 50± Teredinidae. 



/^5 - Intermittent 3.0 ppm, 2 hrs. on, h hrs. off - no borers. 



f^6 - Intermittent 1.5 ppm, 2 hrs. on, 2 hrs. off - no borers. 



M - 2 



