Hand Ditching for Malaria Control

How permanent drainage solves mosquito problem in areas of high mosquito count with reclaimed land offsetting cost of construction. Principles of hand ditch construction. (CDC^-047; 6 minutes, color) Hand Soldering U.S. Office of Education, 1944. (Accessory Assembly Series. Tools and Procedures No. 1) Theory of solde how to prepare irons soldering torches; clean and prepare the work; fasten joints; solder wire and lug joints; and seal seams. Animation. Supplementary filmstrip, same title, also availa