able to find any radioactivity in any of the heavy spars examined by him, and even if he did not specially examine heavy spar from Joaehimsthal, the above result would be strange, since all other experience of the co-occurrence and mutual replacement of the elements would preclude that radium, in contradistinction to calcium and strontium, would be prevented from association with natural barium compounds, if it really were an element closely resembling barium. But if radioactive heavy spar occurs, its radium contents would pass into the barium chloride manufactured therefrom, and in that case it would not be difficult to separate it by fractional crystallizations on a large scale, however minute the radium contents might be. The experiment made by S. Curie with 50 kilos of commercial barium chloride has, however, given a negative result.
But even if radium for reasons at present unknown should exclusively follow the occurrence of uranium, it ought to occur in relatively wide diffusion at least in the Erzgebirge. For even outside of the deposits of pitchblende, such as those of Joachimsthal or of Johanngeorgenstadt, Schneeberg, Annaberg and Freiberg, one finds in the region specified frequently uranium-carrying rocks, especially granites, the uranium contents of which are indicated by an incrustation of calcium uranite acting on the sensitive plate and often visible in the crushed rocks used in the streets. It therefore appears not impossible to find in that region, where also bismuth is widely diffused, a new material which might successfully be worked for the extraction of radioactive substances. By producing radium in the pure state in larger quantities and by the thorough study of its chemical behavior we might possibly not only attain knowledge of the essence of radioactivity, but also place the existence of radioactive elements of individual character and definite chemical behavior beyond doubt.
