Transcriber’s Note

The photographic images in the originalpublication are generally of poor quality and there is little thatcan be done to enhance them. The hand-drawn construction diagramsare clearer although some descriptive text may be too small to read.However the reader can click on any photographic image or diagramto see a larger version. This is particularly helpful when readingdescriptive text and looking at fine detail in the constructiondiagrams.

The cover image was restored by ThiersHalliwell from elements of the original publication and is placed inthe public domain.

See endof this document for details of corrections and other changes.