ciples of sanitary science. We can with truth, therefore, say that the sanitary work on the Isthmus has extended beyond the confines of the Canal Zone and of canal construction, and that its good effects on the whole human race rival those of the canal accomplishment itself.

The very title of the "Department of Sanitation" is indicative of the new era; in the old days there would have been a department of hospitals. The new era gives a department of health and its preservation, of sickness and its prevention and cure, while the old merely gave a department for the care of the sick.

Of some of the numerous activities of the Department of Sanitation, such as the Colon and Ancon hospitals, the system of vital statistics, the control and inspection of foods, the discovery and isolation of infectious diseases, and the handling of accident or emergency cases, we may only note in passing that all are well administered and rank with the best of their class in the world. The phases of the work which interest us more are the control of yellow fever and malaria.

The Americans in Cuba proved that yellow fever was communicated only through the stegomyia mosquito. It had been proved that malaria was communicated through another type of mosquito known as the anopheles. Knowing these facts, the fight against yellow fever resolved itself into several elements: First, to prevent the introduction of yellow fever into the Isthmus by strict quarantine; second, to isolate all yellow fever cases within doubly screened rooms, to pre

vent the stegomyia from gaining access to yellow fever germs and thus gaining the power to communicate it to others; third, to screen all living spaces, so as to prevent access of the dangerous mosquitoes to the well; fourth, to study the habits of the mosquitoes and exterminate them as far as possible, especially those which have been in the presence of yellow fever.

In accordance with these principles, all hospitals, hotels, dwellings and offices were most carefully screened; the yellow fever rooms in the hospitals were separated by screens from the rest of the hospital. Most careful and comprehensive inspections and studies led to the finding of the breeding-places of the dangerous mosquitoes and to the removal of the pools of water. In the cities all open cisterns and accidental lodgments for pools of water were removed. In the open country swamps were drained or filled; extensive systems of ditches were established and maintained; pools that could not be removed were coated with a disinfectant that prevented breeding; underground drains were placed to run off the water before it could ooze to the surface and form pools. Larvicide was liberally distributed on stagnant water that could not be drained; it was manufactured in concentrated form, was carried to the brooks in the mountains, and was arranged to drip automatically on the streams, so that if pools should form, the film of destructive liquid would already be there. Near all habitations, underbrush and grass were cut, so that the sun might dry up possible pools and the mosquitoes be deprived of shade, and perish. Fish were thus experimented with as to their

destructive effect on mosquito larvæ. The cities were cleaned, sewered, paved, and provided with water. In fine, no possible precaution that intelligence and extreme diligence could devise was overlooked.

The result was the banishment of the hitherto prevalent yellow fever, a marked diminution in the amount of malaria, and generally healthful conditions accompanied by a low death rate.

Sanitation work is expensive; the cost, to June 30, 1913, was $16,250,000.

COSTS OF WORK

One of the most effective and widely used means for determining the degree of efficiency in the performance of work is obtained through the careful study and analysis of the costs of work. The commission in 1907 established a very complete system of engineering cost keeping devised for the purpose of disclosing the unit costs of the various elements of work. The cost of excavating in the Culebra Cut for instance, which was referred to in the description of the excavation was computed monthly. The quantities excavated and the amount of supplies used were measured and recorded as well as the moneys expended. Similar records were kept and unit costs determined for the elements of a great variety of operations including dredging and delivering of sand, quarrying and crushing of rock, making of concrete, dredging channels, laying railroad tracks and many other items of work. From these records combined with their knowledge of the conditions, the engineers could determine whether

the work was being done better or worse than in previous periods and also where efforts must be made to bring up the efficiency or where plant changes must be made. The unit costs on the canal work compare very favorably with similar costs elsewhere which is absolute proof, if any be needed, that the various operations were carried on efficiently. A few of the interesting unit costs are as follows:

Excavating Culebra Cut per cu. yd. to June 30, 1909.

$0.9155

Dredging by sea-going suction dredge per cu. yd. fiscal year 1911..

0.0452

It must be remembered that the proper weighing of unit cost records requires experience, knowledge of local conditions and general good judgment. The concrete costs on the Atlantic end were greater, due to the necessarily high production costs of stone and sand. A dredge cutting a shallow layer of material would necessarily be operating at a higher unit of cost than if working on a layer of sufficient thickness to develop the full capacity of the dredge, and a hard sandy clay would cost more to dredge than river mud.

It is interesting to compare the predicted costs of the various branches of the work as made by the minority of the board of consulting engineers and the estimates of the final project made by the commission with the actual records of cost to June 30, 1913, when the great bulk of the work was nearly completed. The following table shows such a comparison:

The differences are large but readily explained. The increases in the 1908 estimate over that of 1906 are principally due to changes in plan resulting in improvements. In the Atlantic Division the locks were made larger and wider and provided with additional gates, the Toro Point breakwater was changed in location and increased in size, the cost of channel excavation was greater, due to larger quantities in earth and rock