Guard-gates near Obispo 455 385. Character and Stability of the Culebra Cut 455 386. Length and Curvature 456 387. Small Diversion-channels 457 388. Principal Items of Work to be Performed 457 389. Lengths of Sections and Elements of Total Cost 458 390. The Twenty Per Cent Allowances for Exigencies 459 391. Value of Plant, Property, and Rights on the Isthmus 460 392. Offer of New Panama Coal Company to Sell for $40,000,000 461 393. Annual Costs of Operation and Maintenance 462 394. Volcanoes and Earthquakes 463 395. Hygienic Conditions on the Two Routes 464 396. Time of Passage Through the Canal 465 397. Time for Completion on the Two Routes 466 398. Industrial and Commercial Value of the Canal 469 399. Comparison of Routes 471 PART I. _ANCIENT CIVIL-ENGINEERING WORKS._ CHAPTER I. =1. Introductory.=—It is a common impression even among civil engineers that their profession is of modern origin, and it is frequently called the youngest of the professions. That impression is erroneous from every point of view. Many engineering works of magnitude and of great importance to the people whom they served were executed in the very dawn of history, and they have been followed by many other works of at least equal magnitude and under circumstances scarcely less noteworthy, of which we have either remains or records. During the lapse of the arts and of almost every process of civilization throughout the darkness of the Middle Ages there was little if any progress made in the art of the engineer, and what little was done was executed almost entirely under the name of architecture. With the revival of intellectual activity and with the development of science the value of its practical application to the growing nations of the civilized world caused the modern profession of civil-engineering to take definite shape and to be known by the name which it now carries, but which was not known to ancient peoples. Unfortunately the beginnings of engineering cannot be traced; there is no historical record running back far enough to render account of the earliest engineering works whose ruins remain as enduring evidence of what was then accomplished.