Page:Popular Science Monthly Volume 65.djvu/193

Rh at present engaged in mapping the spectra in the ultra-violet region. Chemists have agreed to accept an element only when a definite atomic weight and characteristic spark spectrum are had. To be sure such important observations require verification in the hands of others as well.

the high price of cotton is partly due to the abundance of certain insect pests in the south is strikingly shown by the two maps, which we reproduce, showing the distribution in Texas of two of the more important insect enemies of cotton. The bollworm has long been known as injurious to cotton, corn and other crops, in foreign countries as well as in the United States. The Mexican cotton boll weevil, at present the most serious menace to cotton culture, has spread northward from Mexico during the past ten years, until now it occupies the greater part of the Texan cotton belt, and has entered Louisiana. Both of these insects live within the boll or carpel of the cotton plant; and at present there is no way of combating them save by cultural methods. The government has appropriated a considerable sum of money for an investigation of these insects, and a number of scientists, under the Department of Agriculture, are now at work in Texas and Louisiana. The present status of

 Map showing distribution of cotton boll weevil in the United States in 1903. The heavy line indicates the limit of the region in which the weevils have multiplied 10 such an extent as to be found in all cotton fields; the remainder of the shaded portion indicates the region in which colonies are known to exist.