CONTENTS 



Department Bulletin No. 1226. — The Recovery of Potash as a Page 

 By-product in the Blast-Furnace Industry: 



Introduction 1 



Recovery of potash in the cement industry 2 



Method of investigating loss of potash in the blast-furnace industry.. 2 



Reactions within the blast furnace 3 



Classification and sources of iron ores 4 



Blast-furnace fluxes L-_ 5 



Blast-furnace fuels 5 



Factors governing volatilization of potash in blast furnaces 6 



Potash in blast-furnace raw materials and slags 8 



Estimated loss of potash in the blast-furnace industry 15 



Possibility of potash recovery 16 



Summary , 18 



Bibliography 19 



Department Bulletin No. 1227.- — Damage to Range Grasses by 

 the Zuni Prairie Dog: 



Introduction 1 



Vegetation affected '. 3 



The Coconino experiment 4 



The Williams experiment 9 



Some grazing relations of prairie dogs 11 



Summary and conclusions 13 



Literature cited 15 



Department Bulletin No. 1228. — Results of Experiments with 

 Miscellaneous Substances Against the Chicken Mite: 



Introduction 1 



The chicken mite 1 



Kinds of tests made, and methods of estimating the results 1 



Miscellaneous treatments 2 



Dusts 4 



Paints 6 



Sprays 6 



Summary 9 



Recommendations 1 10 



Department Bulletin No. 1229. — The Stem Nematode Tylenchus 

 Dipsaci on Wild Hosts in the Northwest: 



Introduction 1 



Symptoms 1 



The causal organism 2 



Distribution 2 



Apparent independence of the two hosts 3 



Relation to environment 5 



Origin and dissemination of the disease • 5 



Inoculation experiments 7 



Economic significance i 8 



Summary 8 



Literature cited 9 



Department Bulletin No. 1230. — Conditions Affecting the De- 

 mand for Harvest Labor in the Wheat Belt: 



Introduction 1 



Purpose and methods of study 3 



Amounts of labor used in wheat harvest 5 



Effect of different kinds of machinery upon labor demand 14 



Influence of climatic conditions upon harvest labor demand 21 



Usefulness and modification of the Kansas formula for estimating 



harvest labor needed 23 



Labor demand in threshing 24 



Mobilization and distribution of harvest hands 30 



Wages and hours of harvest and threshing hands 32 



Appendix tables 38 



79499D— 28 3 



