FIFTEENTH ANNUAL REPORT 33 



of lime, and rinsing, require a minimum amount of handling 

 of the demijohns, are economical, and with adequate supervision, 

 practically insure sterile containers. These methods are the 

 most successful yet tried and are in use by several companies. 



Information concerning several other phases of water investi- 

 gation is being accumulated. Work on the analysis of Manila 

 rain water shows that in the vicinity of Manila approximately 

 165 kilograms of salt fall annually with the rain on each 

 hectare of ground. Work on the standardization of methods 

 of analysis and in modifying and improving the existing methods 

 is continually in progress. Some data has been accumulated on 

 the changes undergone by water samples bottled under various 

 conditions. Many of the best known Philippine "mineral" 

 springs and baths have been examined for radioactivity. When 

 completed, the results should materially contribute to our knowl- 

 edge of Philippine water supplies and geology and should be 

 of more than local interest. As the result of our examination, 

 one company advertising its bottled water as "containing radium" 

 has discontinued the offending advertising. 



With the cooperation of the Bureau of Public Works a large 

 test fence has been made, apparatus has been constructed and 

 standardized, and iron plates for exposure tests have been pickled 

 and are stored awaiting use. The methods of making paint 

 films and of determining the drying power, tensile strength, 

 elasticity, and porosity of films have been worked out. The 

 work will proceed as soon as the paint materials are furnished 

 by the Bureau of Public Works. 



Work on lumbang oil with respect to its use alone or in mix- 

 tures with linseed oil for paint is in progress. The effect of 

 various dryers has been also studied. 



The new lime kiln was completed during the year, and a begin- 

 ning of the study of the manufacture of lime from Philippine 

 limestone in this experimental kiln has been made. 



A large number of investigations on cement, clays, tie mate- 

 rials, and concrete, including a study of failures of concrete 

 construction throughout the Islands, the behavior of concrete 

 made from certain aggregates obtained locally, and the effect 

 of various electrolytes on cement, are underway. In the assist- 

 ance to the local tanning, in the investigation of galvanized 

 iron, etc., as much has been accomplished as the pressure of 

 more urgent work would permit. Cooperation with the section 

 of botany is mentioned on page 24. There are many lines of 



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