Excerpt from Housecraft Science Dunstan, for permission to use certain diagrams from their books, and for valuable assistance. He is also greatly indebted to Mr. H. H. Green, b.sc., who has revised the proof, to Principal Barker for useful suggestions, and to Messrs. Baird Tatlock who have lent blocks. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.