Insulating materials : vulcabeston controller parts, field spools, bushings, etc. ...
A trade catalogue of insulating materials issued in 1894 by the H. W. Johns Mfg. Co. of New York to sell vulcabeston controller parts, field spools, bushings and sheet insulation to electricians and equipment makers. The engravings are small blue-printed line drawings of turned and molded parts shown in three-quarter view, built up from close hatching and ruled shading, plus flat plates and washers pierced with bolt holes; useful as industrial object silhouettes and as hatching patterns for curved surfaces.
