"The three suburban wards, Jesus del Monte, the Cerro, and Vedado, enjoy the best reputation for salubrity, and also for their freedom from yellow fever. Intelligent residents are readily found, who will assert with great assurance that no one is ever attacked in these wards except those who have been elsewhere infected. The summit of Jesus del Monte has an altitude of 67 meters, or 220 feet, the highest point in Havana, or its immediate vicinity. However, there are few, if any, houses about the summit; the average level of the ward is only 80 feet, and more inhabitants live below than above this level. The natural drainage is excellent, the houses in the elevated portion occupy more ground and are better ventilated than in Havana." GEOLOGICAL FORMATION "The surface soil of Havana consists for the most part of a thin layer of red, yellow, or black earths. At varying depths beneath this, often not exceeding one or two feet, lie the solid rocks. These foundation rocks are (especially in the northern and more modern portion of the city, towards the coast of the sea and not of the harbour) quarternary and especially tertiary formation so permeable that liquids emptied into excavations are absorbed and disappear. In the southern and greater portion of the city, these rocks are of cretaceous formation, and so much less permeable that sinks and other excavations readily fill to overflowing. About twenty thousand persons or one-tenth of the population, live on land reclaimed from the sea, in large measure, by dumping on garbage and street refuse. Much of this reclaimed land was formerly mangrove swamps, and Havana still lies adjacent to these breeders of malarial poison. There are few if any towns in Cuba which are not subjected to malarial effluvia from mangrove or other swamps, and many of these suffer to greater extent than Havana." Messrs. Ariza and Herrera reported a population of 3000 on the reclaimed parts of the first district, 5000 on parts of the third and fourth, 5000 on part of the fifth, and 600 on part of the sixth district. THE CLEANSING OF THE HARBOUR