DEPARTMENT OF AGEICULTUEE BULS. 676-700. 



Department Bulletin No. 681.— Grain-dust Explosions: Investigations 



IN THE Experimental Attrition Mill at Pennsylvania State College: Page. 



Object and scope of the investigation. . ._ 1 



Principles underlying grain-dust explosions 4 



Apparatus used in investigation 6 



Materials used in in^'estigation - - 10 



Experimental v/ork 10 



Experiments from April G, 1916, to October 3, 1917 12 



Discussion of results and conclusions 39 



Summary of conclusions - 48 



Appendix: 



Recommendations for future investigations 49 



Resume of some past explosions 49 



Bibliography - 52 



Department Bulletin No. 682. — A Study of Prices and Quality op Cream- 

 ery Butter: 



Importance of accurate wholesale price quotations 1 



Method and scope of investigations 1 



Wholesale quotations on which creamery butter prices are based 2 



Important basic wholesale butter markets 3 



Relation of wholesale price quotations to standards and grades 5 



Relation of wholesale prices to jobbing and retail prices 9 



Retail price levels 11 



• Effect of packaging under established brands 15 



Effect of differences in type of retailers 16 



Conclusions 20 



Department ^Bulletin No. 683. — Utilization op Elm: 



Importance 1 



Commercial species 1 



Characteristics of the wood 2 



Structure of the wood 6 



Supply and demand 7 



Utilization by industries .• 14 



Grading rules for elm 28 



Lumber and stumpage values 29 



Markets 35 



Elm in the woodlot 37 



Summary and conclusions 38 



Classified uses of elm, in the different wood-using industries 39 



Department Bulletin No. 684. — The Sources of Apple Bitter-rot 

 Infections: 



Introduction 1 



Sources of infection 4 



Mummied fruits 4 



Bitter-rot cankers. 7 



Cankers other than those of bitter-rot 17 



Leaves 18 



Other host plants 19 



Infected fruits of the current year 20 



Relation to control measures 21 



General summary 22 



Literature cited 24 



Department Bulletin No. 685. — Honeybees and Honey Production in 

 THE United States: 



Map indicating distribution of colonies of bees in the United States 2 



Extent of industry 4 



Dependability of tables , 5 



Colonies of beesin the United States 8 



Increase by swarming. 10 



Wintering bees , . . 11 



Losses 15 



Yields of honey per colony 22 



Total production of honey, by decades since 1859 25 



Form of honey produced 27 



Color of honey 30 



