Page:Popular Science Monthly Volume 58.djvu/453

Rh which have been too much neglected by later observers.

geologists were especially interested in a paper by Prof. Frank D. Adams, of McGill University, which gave the results of an investigation on the flow of rocks when subjected to pressure in the laboratory under conditions which reproduce those obtaining in the deeper portions of the earth's crust. Marble was the rock on which most of the work was carried out, but harder rocks, such as granite, are now being studied. Small columns of marble were carefully turned, polished and accurately fitted into heavy wrought iron tubes, constructed on the plan of heavy ordnance by wrapping strips of wrought iron around a core of soft iron and welding the whole together. The core of iron was then bored out and the marble substituted for it. Heavy steel pistons were fitted into each end of the tube, and the rock was submitted to very high pressure, often for several months continuously, in especially constructed machines capable of developing pressures reaching nearly a hundred tons to the square inch. Under high pressures the marble was found to flow, bulging out the iron tube that enclosed it on all sides. When the iron tube was cut away a solid block of marble was obtained, which had completely altered its shape. It was found, however, that the marble in these cases was only about half as strong as the original rock. Other columns of marble were heated to temperatures of 300° C. and 400° C, and while thus heated the pressure was applied as before. Under these conditions the rock was found to flow readily and to retain its strength much better, being nearly as strong as the original rock. In the third series of experiments, the marble was not only heated to the temperatures before mentioned, but at the same time water under a pressure of 460 pounds to the square inch was forced through it while it was being compressed. Under these conditions, the marble, after being molded, was found to be as strong as it was originally. A microscopical study of the structure of the deformed marble shows that in these two latter cases the crystalline grains composing the marble had glided on one another.

the papers presented before the Bacteriological Society one of the most interesting was by H. L. Russell and S. F. Babcock, of Madison, Wis., upon the causes effective in the production of silage. The very great influence of bacteria in natural processes has led in the last few years to an assumption on the part of bacteriologists that these micro-organisms are agents in nearly all the general processes of nature involving chemical change. Among other phenomena connected with agriculture, it has been claimed that the changes which take place in corn fodder in the farmer's silo are the result of the growth of bacteria. These changes are accompanied by a rapid heating of the material when first placed in the silo and, later, by the production of peculiar flavors and aromas. These phenomena are so similar to those which bacteria are known to produce that it has been a very natural assumption that they are caused by micro-organisms. Russell and Babcock have been of the opinion that bacteriologists have gone too far in ascribing natural phenomena to bacterial agencies, and that it is necessary to look in different directions for the explanation of some of them. The production of silage, for example, they insist, is not the result of bacterial action. By carefully performed experiments they succeeded in producing normal silage under conditions in which bacterial growth was prevented. They conclude that the changes occurring in silage are produced partly by a continuation of the respiratory activities of the plant cells, which, for a time, are stimulated rather than checked when the plants are cut to pieces for storing in the silage, and partly as the result of the action of certain chemical ferments or enzymes, which are eliminated