8vo. 14 folding maps, many with hand coloring. (Ca 5-in. tear to first map, a few maps with other short tears to folds.) Original green cloth gilt (some very slight rubbing to extremities). 

FIRST EDITION, AUTHOR'S PRESENTATION COPY with his compliments slip tipped in.  This portfolio was published to accompany a report issued by the local transportation company of the Chicago City Council. Arnold developed a new method to convert alternating current from power plants to direct current in substations for the Chicago & Milwaukee Electric Railway.  He later assisted the New York Central Railroad and the Hudson River Railroad in converting their lines leading into Grand Central Terminal.