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caesium vapor would be especially important as it would show whether the relations mentioned apply to this metal as well. Of course there would be serious difficulties in carrying out such a n investigation for these vapors attack almost all vessels.” I n the second section of the volume, the author considers the question of stability and finds t h a t there are well-defined critical temperatures and t h a t these temperatures are raised by the addition of small amounts of a non-colloidal third substance. The third section deals with the Brownian movements. The author gives the particles a constant movement in one direction, thus changing the oscillations into a wave-form of curve. This simplifies the measurements and the author finds t h a t the velocity of the particles is about one hundred times t h a t of the electrical migration under a potential drop of one volt per centimeter. He therefore considers t h a t the Brownian movements cannot be the result of electrical phenomena. After considering other possibilities, the author decides t h a t the Brownian movements are due to the actual oscillations of the molecules as required by the kinetic theory of gases. Whether one accepts this last conclusion or not, there is no question but t h a t this is a very important investigation, and one which reflects great credit Il‘ilder D . Bancrojt on the author. Oeuvres de Pierre Curie, PuhliBes p a r les Soins dc la Socidtd F r a q a i s e de Physique. 16 X 25 cm; p p . xrii + 6 2 1 . Paris: Gauthieu-1-illars, 1908. Price: @ p e r , 2 2 fruzcs.-This volume of six hundred pages contains the complete works of Pierre Curie. At first sight this does not seem a large output for a n active scientific career extending over twenty-seven years ; b u t the work is not of a kind to be measured by pages. Xt no time did Curie have a large number of students or a n adequately equipped laboratory. XI1 his life he interested himself in difficult problems of such a nature t h a t the results of a great deal of v o r k could be presented in relatively few words. The work on crystallography and on radioactivity may serve as an illustration. Then, too, Curie vias a man who thought long about a subject before he published anything on it, and if some one anticipated him he did not publish at all. I t is a matter of opinion whether an intense yearning for perfection in each publication is a n unmixed blessing; b u t one cannot help admiring the man \Tho has it and who lives up to i t in these days when so many of us go to the opposite extreme. Curie’s papers deal n i t h four general topics : crystallography ; reduced equations; magnetism; and radioactivity. The last group is the one which has attracted t h e most attention and on which Curie vias working when his career was c u t short; b u t i t would be a great mistake to consider the earlier work as unimportant. To take but a single instance, the paper on the magnetic properties of substances a t different temperatures is a masterly piece of work and will some d a y receive a great deal more attention than has yet been bestowed upon it. The whole world is familiar with the details of Curie’s untimely death; b u t i t has not known until now, about his unsatisfied longings for more adequate facilities. It is pathetic the way in which Curie vias offered decorations when 1l;ilder D . Baiicrojt what he wanted was a laboratory.
