TWELFTH ANNUAL REPORT 73 



this, a greater part of the force would be idle about half of the 

 time. Our capacity soon will be 65 samples per day, or 16,250 

 samples per year of 250 work days. This will enable us to turn 

 out about 1,400 tests a month, and it seems that, with a little care 

 and judgment on the part of those most responsible for the pur- 

 chase and use of Portland cement, the swamping of our force 

 could be avoided. Obviously, we could increase the testing ca- 

 pacity to any desired figure ; not, however, without a correspond- 

 ingly large additional cost to the Government. 



While there has not been a corresponding increase in the 

 demand for tests of road materials, the work now done on each 

 sample is much greater than when it was customary to request 

 only an abrasion test. . Local engineers now demand a complete 

 examination, including abrasion, hardness, toughness, cementive 

 value, fracture, and classification; and lately they are giving 

 consideration to the chemical and physical properties of tars, 

 asphalts, bitumens, and oils intended for use on local roads. 



The Bureau of Science has pointed out the advisability of a 

 more systematic and cooperative study of the efficiency of avail- 

 able road materials under actual conditions of local climate and 

 traffic, but little has been done along this line so far as we know. 



It frequently happens that a request for information concern- 

 ing the composition, value, or utility of a sample involves a 

 lengthy and complicated examination. At other times a correct 

 interpretation of the results obtained cannot be given without 

 much study and considerable research work. Among such re- 

 quests received during the past year were the following: 



1. To state from the results of analyses the relative efficiency of different 

 kinds of prepared bituminous roofing felts. 



2. To determine the suitability of 23 different raw materials for the 

 manufacture of Portland cement. This involves a great amount of work 

 as it is necessary not only to analyze each material, burn the most promising 

 mixtures obtainable from the same, and subject the final product to routine 

 test, but also to study the effects of different degrees of liming, burning, 

 seasoning, and plastering. 



3. To determine from the results of analyses the relative efficiency of dif- 

 ferent kinds of paints and protective coatings, taking into consideration the 

 local conditions such as are met with according to whether the material 

 is subjected to the action of sea water, fresh water, or air. 



4. To ascertain a practical method for bleaching low-grade hemp fibers 

 and rope, Malacca cane, etc. 



5. To determine the cause of foreign deposits in the product of a local 

 artificial ice plant. 



6. To solve problems connected with the creosoting of local timber. 



7. To determine the cause of the rapid corrosion of certain kinds of iron 

 and other metallic structural materials. 



