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eddies of air which move forward with the storm, chiefly along the edge of it. An argument in favor of this is the precipitation of hail over comparatively narrow belts. Such eddies are formed hy the sudden uprushing of overheated moist masses of air into the high very cold levels during thunder storms, and also during the general disturbance of atmospheric equilibrium when a cold wind from above passes over the hotter lower layers of the atmosphere. Similar eddies often pass along the surface of contact hetxeen hot and cold layers of air, the phenomenon often being repeated a number of times. “Ferrel considers t h a t hailstones are formed in very violent uprushing eddies of air having small cross-sections, and he assumes that the xnall hailstones are vhirled upward repeatedly until their \\.eight has become so great t h a t they fall to the earth. The velocities called for in the eddies are not irnprohahle ones when we consider the effects produced h y local eddies, such as 1l.ilder D . Ha~zcrojt cyclones and tornadoes, even a t the earth’s surface.” Dr. I. Frick’s Physikalische Technik oder .In l e i t u n g zu Erpcr2‘iifciital;orfI U Y S~lbstiierstelliing eiiifaclier Demo,zsfrati~,zsuppa~ate.Sz‘ehciitc ~ o l k o m n t e i z iiingmrbeitefe u n d stark nernzchrtc .Iu,dage i o i i U r . O t f o Leirmutzi>. Zweiter Band. Ersfe .4btci!ztng. 18 X 26 cin; fip. .&z 762. Braunscii7;~eig: Friedrich I’ie;,eg 1 1 1 1 d Soiin, 1907. I’ricc: paper, 20; bourid, 22 mavks.--.\s the title itself shows. this hook is intended to be uf service to the lecturer jn physics both by showing just how certain experiments can lie performed and also I,? telling him from what firms he can h u y special apparatus for the experiments. The hook is eminently successful in both aims. The experiments in this volume are grouped under the headings: electrostatics; galvanism ; magnetism ; induction. There is a n extraordinary number of experiments and they are vary well chosen. Some of them are distinctly interesting for reasons other than their merit as lecture experiments. T h u s on p. 280 we find the statement that v h e n lead is precipitated electrolytically from a n aqueous solution, hexagonal crystals are obtained with a low current density and regular crystals with a higher current density. There are several experiments on the heliavior of isolated conductors in :in electrolytic solution through which a current is passing; but they deal chiefly with the special case of no polarization a t the surface of the interposed conductor. The revie\ver has always liked the experiment of the precipitation of copper from a copper sulpliate solution on a detached carbon rod the moment the fall of potential in tlie solution alongside of tlie rod exceeds a certain value. l l ’ i l d e ~D . Hancrojf rageii sowic
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Elementary Agricultural Chemistry. A Handbook for Junior Agricultural Students and Farmers. B y Herbert Ingle, 13 X 20 cm; pp. ix f 250. London: Charles Griffin and Company. Philadelphia: J . B. Ta,zppincott Company, 1908. Price: $1.50 net,-In the preface the author says: “This little volume is based upon the writer’s long experience in teaching agricultural students, among whom there are, unfortunately, many who cannot devote the time necessary t o acquire sufficient knowledge of pure chemistry t o profitably read such works a s the author’s Manual of Agricultural Chemistry.
