For the greatest difficulty the Americans have had to contend with has been the climatic conditions so fatal to the workers during the construction of the Panama Railway in 1850, and throughout the operations of the two ill-fated French Canal Companies. The careful attention which the Health Department of the Canal Commission has given to the sanitation and purification of their new territory, as well as of the towns of Colon and Panama, has amply justified the enormous expense by the wonderful results obtained. When one considers that yellow fever has always been regarded by tropical Americans as indigenous to their climate, it is indeed surprising that this disease has been practically exterminated from the isthmus of Panama in so short a time. Houses have been entered, cleansed and fumigated; marshes drained, stagnant water treated with petroleum and the bush and scrub around all dwelling houses cut away, until haunt and breeding ground are alike denied to the germ-bearing mosquito. Everywhere one comes across members of the Sanitary Corps, either lowly negroes and half-bred Indians with cans of petroleum from which they drop a small quantity of oil on any stray pool or puddle that they come to; or the doctors ever vigilant in their inspections of the most out-of-the-way holes and corners in which dirt or disease might lurk. [Illustration: A CAMP AT BALBOA.] The large hospital at Colon, built upon piles over the seashore, was erected originally by the French, but has been improved and modernised until it is as well equipped as any similar institution. There has not been a case of yellow fever within its walls for some years now, and the many screens that formerly were placed around the beds have all been stored away, except one, left as a specimen to show visitors the methods employed in isolating patients suffering from the dread disease. Colon has changed very much during the last ten years. The fires of 1885 and 1890 destroyed a great many of the wooden buildings of which it was formerly composed; and the only old buildings of any pretensions to durability are the railway station and offices, and a church which was built by the pioneers of the isthmian route in the middle of the last century. Reorganised and rebuilt for the purposes of the Atlantic terminus of the canal, the most prominent features of the town to-day are the large wharves and warehouses for the reception of the materials and supplies for the vast project. Laundries, bakeries, schools, court-houses and administration buildings, dwellings for employees, hotels, stores and machine shops, have been erected on this erstwhile mangrove swamp, an undertaking in itself of great magnitude.