Page:Popular Science Monthly Volume 23.djvu/437

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author of this manual has aimed to produce a guide for those who, having had no previous training in chemical work, wish to learn assaying. Hence, he gives first full descriptions of the apparatus required, generally with illustrations, names of makers, and prices. The reagents are as fully described, and, wherever necessary, methods of preparing and testing them are given. The processes of assaying are detailed with great clearness, from the crushing of the ore to the estimation of its value per ton, and in the appendix are given various special methods of assay, lists of minerals likely to contain gold, silver, copper, or lead, a list of books on assaying, various departments of chemistry, mineralogy, mining law, etc., and useful tables. The volume is got up in much better style than is usual with scientific and technical manuals.

expediency of using kerosene has been disputed, chiefly on account of the danger of its injuring the plants. The objection is applicable to pure kerosene, and with greater force as regards some species than others. Professor Riley advises that kerosene be used with caution where its effects are not already known, and never be employed pure. With this reservation, his own experience and that of his assistants shows that neither lye nor whale-oil soap, the other substances recommended, "bears comparison with an effectual kerosene emulsion as an effectual destroyer of scale-insects and their eggs."

paper was prepared with particular reference to the city of Peoria, and was read by request, in December last, before the Scientific Association of that place. It is the fruit of many years of observation and much careful study, and consists chiefly of notes on native species and their adaptability to the soil, climate, and situation of Peoria, with directions for their cultivation and care. Much of it is applicable to other places than Peoria.

is the final report of the survey, begun in 1841, of the Northern and Northwestern lakes. The work is described under the headings, "Standards of Length, Bases, and Base Apparatus." "Primary Triangulation," "Astronomical Determinations," and "Principal Results of the Geodetic Work." A short history of the survey is prefixed to the volume.

this volume is begun the publication of a series of papers whose objects are "a systematic determination of the constants of astronomy from the best existing data, a reinvestigation of the theories of the celestial motions, and the preparation of tables, formulae, and precepts for the construction of ephemerides, and for other applications of the results." The present volume contains papers on the "Recurrence of Solar Eclipses," "Hansen's Lunar Theory," "A Determination of the Velocity of Light," "A Catalogue of 1,098 Standard Clock and Zodiacal Stars," on "Gauss's Method of computing Secular Perturbations," and a "Discussion of Transits of Mercury from 1677 to 1881"

wants to know all about the bacteria which have been found to play so