Page:Popular Science Monthly Volume 32.djvu/143

Rh and the special hurtful resistances to motion, the calculations of which have hitherto been confined to the analytical method. No method being known to the author by which the frictional resistances and efficiency of any desired mechanism can be graphically determined, he has endeavored, in his lectures before the polytechnic schools of Aix-la-Chapelle, to show the relations existing between the forces in mechanism in a simpler form than that offered by the analytical method. The present treatise, which the translator characterizes as containing "almost discoveries" on the subject, has grown out of that endeavor.

practical manual on the application of gun-cotton, which rests largely upon the evidence of more or less extensive experiments performed in Germany, is preceded by an account of the manufacture, properties, and uses of modern gun-cotton, by Lieutenant John P. Wisser, of the United States Army.

family of Syrphidæ is one of the most extensive in the order of Diptera. "They contain among them many of the brightest-colored flies, and numerous specimens are sure to appear in every general collection of insects. None are injurious in their habits to man's economy, and many of them are very beneficial." To be more definite in popular description—"they are flower-flies, and feed upon honey and pollen. They are observed on blossoms of sweet-smelling, melliferous plants, such as the Hymenoptera prefer; and patches in bloom of blackberry (Rubus), wild-cherry (Prunus), dogwood (Cornius), Canada thistle (Cirsium), and elderberry (Sambucus), will always be sure to reward the patience of the collector. Some species, as those of Syritta, Spærophoria, Mesograpta, etc., will be seen wherever there are blossoms. Species of the last, especially, are very abundant about cornfields when the plants are in blossom, and will frequently alight upon one's hands; these 'sweat-flies' are feared by not a few persons, under the belief that they will 'sting.' All are sunshine-loving, and will rarely be found except in the middle of bright, unclouded days." About three hundred species are described in this volume from the region north of Mexico, in such a way that the author hopes that even the non-entomological student, with a little exertion, may be able to identify them.

believes that electricity is a valuable agent in treatment, which had, however, in his practice failed to give uniformly satisfactory results. He set himself to work to investigate the causes of the diversity in the efficiency of its application, and publishes his experiments and the results of them in the present paper. His decided success—in the treatment of pelvic disorders—in the past year, "no longer accidental, but the result of method"—has convinced him of the value of the remedy, which he is assured, when fully developed, will assume prominence. Its success and general adoption, he believes, depends upon precision and uniformity of measure and record; and he has given here, as a contribution to those factors, his own system, which includes the milli-ampère intensity of the current; size of electrodes for calculation of density; time of application, for calculation of quantity; resistance of the tissues in ohms when such resistance was unusual, or when an explanation of the intensity of the current seemed called for.

monograph is one of the Johns Hopkins "University Studies in Historical and Political Science." The "Studies" are now in their fifth series, which is especially devoted to the subjects of municipal government and economics. The history of St. Louis is given from its foundation in 1764, with the various steps of its growth as an infant settlement, a community, a