Page:Popular Science Monthly Volume 40.djvu/441

Rh be said to have come up to a fair average. The presidential address of Dr. Huggins was a learned and able exposition of the spectroscopic and photographic investigation of the sky and of the results accruing from it. The addresses of the presidents of sections were mostly historical or special in character, and lacked the abundance of features of living interest that have marked some of the like addresses in past years. In the Section of Physics and Astronomy Prof. Lodge described his investigations as to the behavior of the ether in the presence of rapidly moving bodies, which, without leading to determinate results, indicated that the ether was not affected by them. A noteworthy paper read in this section was that of Prof. H. A. Newton on The Action exercised by the Planets on the Meteorites of our System. In the Chemical Section Prof. Roberts Austen invoked more attention to the metallurgical branch of the subject, and presented the problems, practical and scientific, with which the metallurgist has to deal. The alloys especially were spoken of as offering a profitable field, and "traces" as possibly having a more important bearing on the properties of the substances in which they are found than has been supposed. The address of Prof. Rupert Jones in the Geological Section related to coal, and showed that further investigation is still desirable in tracing the true origin of the coal-beds, and the ages to which their materials originally belonged. Francis Darwin spoke in the Botanical Section on Growth Curvatures in Plants, and gave the results of his long and minute investigations on the subject. Mr. E. G. Ravenstein presented to the Geographical Section an account of the progress of cartography and a justification of geography as a distinct and profitable branch of inquiry. Some of the most interesting papers read at the meeting were presented in this section by women: an account of her journey to Kilima Njaro, by Mrs. French Sheldon, and Mrs. Bishop's (Miss Isabella Bird) account of her observations in the Bakhtiari country. Prof. Cunningham, in the Section of Economics, stated some problems of high importance in that science; while in the Mechanical Section Mr. Foster Brown's address dealt mainly with details as to recent mechanical inventions; and Prof. Max Müller, in the Section of Anthropology, demonstrated the complexity of the problems of ethnical relationships, and showed that no one class of data, whether of language or physiology, or other, is competent alone for their solu tion. The next meeting of the Association will be held at Edinburgh, with Sir Archibald Geikie as president, August 3, 1892.

Tests of Paper.—Paper lends itself to many frauds which it is of interest to be able to detect; and it is desirable to know how to measure its principal quality—resistance to tearing. The processes for determining these conditions are very simple. There are also special details with which few are acquainted. Important differences are noted between machine-made and handmade paper. In machine-made paper the resistance to tearing and the quality of extensibility vary according as the force is exerted lengthwise or crosswise; the difference is in the proportion of two to five. The resistance is greater in the direction of the length, while extensibility is greater in that of the breadth. The differences are explained by the method of making paper by machinery. The veins of fluid running out from the reservoir extend themselves along the metallic network without any real tendency to associate themselves closely with the neighboring veins, while the current lengthens the fibers and felts them in the direction of the length. In hand-making, the paper is homogeneous, equally resistant in both directions—a demonstration of the superiority of hand-work. There is no drawing out and felting in one direction, to the exclusion of the other; but the felting is equally distributed over the whole surface. Machine-made papers can not be stretched much in the direction of their length, for the method of fabrication has already stretched them to near the extreme limit of extension. The simplest means of testing the durability of paper as against the usual mechanical agents of destruction is rubbing it between the hands. After such treatment poor paper is full of cracks and holes, while strong paper simply takes the appearance of leather. The experiment also tells something of the composition of the paper. If much white dust is produced, we know that the paper contains earthy impurities;