400 Scientific Intelligence. 



3. Radio-activity. — Marckayald has recently delivered a lecture 

 before the German Chemical Society giving a good account of 

 what has been done in the field of radio-activity, and discussing 

 the prevailing views in regard to this subject. While this lecture 

 contains little that is new to those who are familiar with the 

 literature of the subject, it will be useful to those who desire a 

 general knowledge of this new branch of science. The author 

 gives a somewhat novel view of the enormous energy involved in 

 the transformation of the radio-active elements by saying : " It 

 was the dream of the alchemists to transmute base metals into 

 noble ones. The radio-active substances teach us that, if this 

 process could be achieved, there would either be obtained at the 

 same time so much energy that in comparison to it the value of 

 the noble metal would be insignificant, or on the other hand the 

 consumption of energy would render the ennobling of the metal 

 practically uneconomical." — Berichte, xli, 1524. h. l. av. 



4. A Simple Method for Determining Vapor Densities. — 

 Blackman" has devised an apparatus for this determination, which 

 consists of a sealed tube in which is plaee'd a capillary tube 

 graduated in millimeters, closed at one end, and supplied with a 

 thread of mercury at the other end in order that it may serve as 

 a manometer. It is evident that when this system is heated with 

 nothing but air within and without the manometer the pressures 

 will continually balance each other ; but in the operation of deter- 

 mining a vapor density a weighed amount of volatile substance 

 is placed in the sealed tube with the manometer, and when this 

 substance is volatilized by heating it exerts a pressure which can 

 be measured by the movement of the thread of mercury in the 

 capillary manometer. Then, when the two temperatures and the 

 volume of the apparatus are known, the vapor density of the sub- 

 stance can be calculated from the pressure produced by it. The 

 calculations are somewhat complicated, and the execution of the 

 operation does not appear to be as simple with this apparatus as 

 with that of Victor Meyer ; but the method is interesting in its 

 novelty. — Zeitschr. physikal. Chem., Ixiii, 48. h. l. w. 



II. Geology. 



1. La Montague Pelee apres ses Eruptions ; par A. Laceoix. 

 4°, pp. 136, figs. 321, Paris, 1908 (pub. by the Academy of Sci- 

 ences). — This is a supplement to the author's great work La 

 Montague Pelee et ses Eruptions, published a few years ago and 

 noticed in this Journal (vol. xix, 465). From a variety of sources 

 the writer has collected a considerable body of facts, which 

 interpreted by the light of his former investigations, he uses to 

 describe the progressive changes which have occurred in the 

 diminishing volcanic activity, and in topography, owing to 

 erosion and the crumbling of the dome of lava. Very interesting 

 are the views showing the rapid growth of vegetation everywhere 



