CONTENTS. vn 



To /ac< 



22. iiiishiiiaii puiiitini;> 573 



23. Trades scliools as aids to industr\- 584 



24. Trades schools as aids to industry 585 



25. Trades schools as aids to industry 592 



26. Trades schools as aids to industry 593 



27. Trades schools as aids to industry 597 



28. A hydrocyanic acid sas generator 6^0 



29. A hydrocyanic acid ?as generator 620 





