The city of Brownsville lies on the left bank of the Rio Grande, about ten miles from the mouth. It has a population locally estimated to be about 8,000 (6,305 according to the census of 1900), of which a large portion is Mexican. The city has no public water supply, in consequence of which river water is hauled in water carts and kept in barrels and tanks and is in very general use for all purposes, except by the better-to-do portion of the population, which obtains its drinking water from the rain water of cisterns. These water receptacles serve, of course, as excellent breeding places for the<i>Stegomyia calopus</i>and the<i>Culex pipiens</i>mosquitoes, both of which were very much in evidence. Although there is no sewerage, the natural drainage into the river is sufficient to carry off the storm water rapidly, so that we observed no stagnant water in