208 



NEGRETTI AND ZAMBRA, HOLBORN VIADUCT, E.G., 



FIG. 14. 



FIG. 10. FIG. 11. 



E. BOURDON'S HYDRAULIC GAUGES. 



FIG. 12. 



FIG. 16. FIG. 13. FIG. 15. 



E. BOURDON'S STANDARD AND DUPLEX GAUGES. 



611 



FIG. 18. FIG. 17. 



E. BOURDON'S DOUBLE AND REGISTERING GAUGES. 



