In December, 1916, Secretary Daniels expressed a desire that Mr. Edison visit him in Washington for an important conference. At that time it seemed almost inevitable that the United States would be drawn into the conflict with Germany sooner or later, and at the conference Secretary Daniels asked Edison to devote more of his time to the country by undertaking experiments on a series of problems, a list of which was handed to him. Edison signified his assent, agreeing to give his whole time to the government without charge, and returned to his laboratory. He immediately put everything else aside, and with characteristic enthusiasm and energy delved into the work he had undertaken. The problems referred to covered a wide range of the sciences and arts, and time being an essential element, he added to his laboratory staff by gathering together from various sources a number of young men, experts in various lines, to assist him in his investigations. Inasmuch as Edison's war work for the government occupied his entire time for upward of two years, it is manifestly out of the question to narrate the details within the limits of a chapter. We must, therefore, be content to itemize the principal problems upon which he occupied himself and assistants and as to which he reported definite results to Washington. The items are as follows: 1. Locating position of guns by sound-ranging. 2. Detecting submarines by sound from moving vessels. 3. Detecting on moving vessels the discharge of torpedoes by submarines. 4. Quick turning of ships. 5. Strategic plans for saving cargo boats from submarines. 6. Collision mats. 7. Taking merchant-ships out of mined harbors. 8. Oleum cloud shells. 9. Camouflaging ships and burning anthracite. 10. More power for torpedoes. 11. Coast patrol by submarine buoys. 12. Destroying periscopes with machine-guns. 13. Cartridge for taking soundings. 14. Sailing-lights for convoys. 15. Smudging sky-line. 16. Obstructing torpedoes with nets. 17. Under-water search-light. 18. High-speed signaling with search-lights. 19. Water-penetrating projectile. 20. Airplane detection. 21. Observing periscopes in silhouette. 22. Steamship decoys. 23. Zigzagging. 24. Reducing rolling of warships. 25. Obtaining nitrogen from the air. 26. Stability of submerged submarines. 27. Hydrogen detector for submarines. 28. Induction balance for submarine detection. 29. Turbine head for projectile. 30. Protecting observers from smoke-stack gas. 31. Mining Zeebrugge harbor. 32. Blinding submarines and periscopes. 33. Mirror-reflection system for warships. 34. Device for look-out men. 35. Extinguishing fires in coal bunkers. 36. Telephone system on ships. 37. Extension ladder for spotting-top. 38. Preserving submarine and other guns from rust. 39. Freeing range-finder from spray. 40. Smudging periscopes. 41. Night glass. 42. Re-acting shell.