232 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



vested, dried, and passed through the experimental retorts, where 

 the kelp has been charred with the evolution of combustible gas, am- 

 monia, and tar. Apparatus for the leaching of the char and the 

 evaporation of the resulting brine was installed during the latter 

 months of the fiscal year, but is not yet operating with entire satis- 

 faction. It is believed that the evaporation of the brine will not 

 involve serious difficulties, as evaporation of similar brines is being 

 carried on satisfactorily at several commercial plants. The new 

 apparatus for effecting a satisfactory leaching of the char is at pres- 

 ent being installed at the plant. Large amounts of dried kelp and 

 kelp char have been sold on their potash content at the market price, 

 ancl $25,894 has been realized from this source. During the latter 

 half of the year a chemist has been employed constantly on the 

 examination of the tar and other distillates from the retorts in the 

 effort to determine the best retorting conditions and the possible by- 

 products recoverable from this source. With the practical comple- 

 tion of the plant it is believed that during the current fiscal year very 

 important progress will be made in demonstrating whether or not it is 

 commercially feasible to extract potash from the Pacific coast kelps. 



It is gratifying to record that studies of the kelp plant during 

 the year seem to show definitely that the kelp beds are actually im- 

 proved by cutting off the mature growth. In southern California 

 it has been demonstrated that beds which have been cut clean renew 

 themselves and are ready for cutting again within three or four 

 months. The disease which caused the total disappearance of certain 

 bed;: in southern California waters a year ago has not appeared dur- 

 ing the past summer in such degree as during the previous season, 

 and operations have nowhere been seriously hampered by this cause. 

 It is believed that prompt cutting of an infected bed has the effect 

 of staying the progress of the disease. 



The usual large number of samples of supposed fertilizer materials 

 have been received by the division during the year and examined, and 

 a large volume of correspondence on fertilizer matters has also been 

 handled. 



SOIL PHYSICS. 



The personnel of the soil physics laboratory has been utilized as 

 much as possible on war problems, only sufficient force necessary for 

 routine analyses being maintained on this work. The other members 

 of the division have been engaged on work on the synthesis of am- 

 monia and the oxidation of ammonia, carried on in cooperation with 

 the Division of Fertilizer Resources of this bureau and the Nitrate 

 Division of the Department of Ordnance, United States Army. The 

 production of synthetic ammonia is of fundamental importance from 

 both a munition and a fertilizer standpoint, and is an emergency 

 problem to the Ordnance Department. The work done in the Arling- 

 ton laboratory has advanced far toward the solving of this problem. 



