Page:Popular Science Monthly Volume 33.djvu/291

Rh States, the necessity of providing by law for the admission of students that have taken scientific courses in statistics as honorary attachés of or clerks to be employed in the practical work of statistical offices. This can be very easily done without expenditure by the Government and with the very best economic results. We take a census of the United States every ten years, but, as a rule, the men that are brought into the work know nothing of statistics. They should be trained in the very elementary work of the census-taking and of statistical science. How much more economical for the Government to keep its experienced statisticians busily employed in the interim of census taking, even if they do no more than study forms, methods, and analyses connected with the presentation of the facts of the preceding census! Money would be saved, results would be more thoroughly appreciated, and problems would be solved."

Plant-Lice and their Insect Enemies.—Two features in the life of plant-lice are the enormous rate at which they multiply, and the suddenness with which they sometimes disappear. The cherry-trees may be black with them in May, and in a month hardly a specimen of them will be found. This welcome riddance is due to their insect enemies. A syphus maggot with a pointed head, says Mr. A. J. Cook, of the Agricultural College, Michigan, just revels in plant lice. It seems never satiated, and it is hard to understand how so small an insect can make so large a meal. The lady-birds, and especially their larva; or grubs, do signal service in the same direction. Several species of the genus Aphidius of the ichneumon family, very minute parasites, destroy the lice by the thousands. Thus, plant-lice on out-door vegetation, which may threaten dire mischief early in the spring, are almost vanquished before summer comes. In some years, however, probably favored by drought, the plant-lice live out of proportion, and succeed in spite of their enemies, when they do most serious injury. They are sometimes favored, too, by misguided cultivators, who destroy their enemies, mistaking them for mischievous insects. The aphides may be destroyed by the kerosene-and-soap mixture, which consists of a quarter of a pound of hard soap or a quart of soft soap, and a quart of water, heated till the soap is dissolved, to which a pint of kerosene is added, and the whole agitated till a permanent emulsion or mixture is formed. It is applied with a force-pump, of which some are made for the purpose.

Monuments, Sculptures, and Inscriptions at Copan.—Mr. A. P. Maudsley has made a systematic examination of the principal ruins of the ancient city of Copan, in Central America, one of the most interesting of the sites explored and described by Stephens in his first account of his investigations. Mr. Maudsley's examination included surveys and measurements of the mounds, excavations, and the taking of casts, which will be preserved in the South Kensington Museum. He believes that the nature of the structures has been in some points mistaken; that the so-called pyramids are the raised foundations which sup ported roofed buildings—probably temples—which were approached by steep flights of steps; that the long heaps of stones which were taken to be the ruins of city walls are in fact the remains of single chambered, stone-roofed houses; and that the great "river-wall" is merely a wall in appearance, resulting from the river having changed its course and eaten into the raised terraces and lofty foundations on the east side of the ruins, the plan of the structure on that side having been originally the same as on the other sides, with slopes and stairways. A few worked stones, including some beads and a whorl of jade, pearls, and carved pieces of shell, a pot containing red powder and several ounces of quicksilver, human bones, dog's teeth, and skeletons of jaguars, parts of one of which were painted red, were found in the excavations. Mr. Maudsley adduces evidence, from the failure of all the Spanish chroniclers to make any mention of the cities which these ruins represent, or of anything like them, and from the comparison of the ruins with what the Spaniards did speak of, that the sites had been deserted, and the buildings buried in the forest and lost, long before the time of the conquest. The ruins of Copan have been famous ever since Stephens made them known, for the profusion of sculptured