Papers on subjects connected with the duties of the Corps of Royal Engineers : Vol. VI Papers on subjects connected with the duties of the Corps of Royal Engineers : Vol. VII Papers on subjects connected with the duties of the Corps of Royal Engineers : Vol. VIII Papers on subjects connected with the duties of the Corps of Royal Engineers : Vol. X Papers on subjects connected with the duties of the Corps of Royal Engineers : Vol. XI Papers on subjects connected with the duties of the Corps of Royal Engineers : Vol. XXI