August 19, 1887.] 



SCIENCE. 



87 



It is striking evidence of the great velocity attained in tornadoes 

 tliat straws and bits of hay are often driven like darts into pine 

 boards, and even into the dense bark of hickory-trees. Professor 

 Mees found, that, to obtain similar results by shooting straws 

 from an air-gun, velocities of from one hundred and fifty to one 

 hundred and se\'enty-five miles per hour were necessar)'. 



Professor Mendenhall read a paper giving an account of the 

 changes in the electrical condition of the atmosphere that are ob- 

 sen'ed during thunder-storms, and referred to the excellent work 

 done by the New England Meteorological Society in the study of 

 these most interesting phenomena. 



Prof. E. S. Nichols gave an account of a battery-cell on which he 

 and Mr. W. S. Franklin had been exp^.finjenting, in which both 

 electrodes were iron ; but one was in a magnetic field, and the 

 other not. The magnetized electrode was found to be sometimes 

 electro-positive to the other, and sometimes electro-negative, de- 

 pending on whether its magnetic poles were exposed to the liquid, 

 or whether the neutral part alone was so exposed. A difference 

 was also found between those liquids tending to produce ferric salts 

 and those forming ferrous compounds. 



Professor Barker presented two papers on behalf of Mr. Edison, 

 in one of which a magnetic balance similar in principle to Wheat- 

 stone's bridge was described, by which the relative magnetic 

 permeabilities of different samples of iron can be rapidly tested. In 

 the other paper, Mr. Edison described an ingenious form of ap- 

 paratus, which he calls a ' pyro-electric dynamo,' in which an 

 electric current is obtained directly from heat-energy through the 

 induction produced by alternately heating and cooling an iron core 

 placed in a strong magnetic field and surrounded by an insulated 

 coil. 



Mr. C. E. Monroe presented to the section the results of some 

 curious experiments in which blocks of gun-cotton, after having 

 been stamped with certain letters, were exploded on flat plates of 

 wrought iron. The gun-cotton blocks were placed with the lettered 

 side down, and it was found, that, when the letters were stamped 

 in relief, they appeared in relief on the iron after the explosion, 

 and, on the other hand, when the letters were depressed in the gun- 

 cotton, they were also depressed on the iron plate. 



The session this year has been of considerable interest, and the 

 number of communications presented to the section unusually 

 large. 



Section C. 



{^Report not received in time for this issiee^ 



Section D. 



Nineteen papers or subjects were presented during the sessions 

 of this section by twelve gentlemen, as follows : on Nicaraguan 

 woods, and friction of engines, by R. H. Thurston ; on the Ameri- 

 can system of water-purification, by Albert R. Leeds; a new 

 method of finding an equivalent uniform load, producing bending 

 moments approximately ecjual to the maximum moments under a 

 moving train, the deflection of girders and trusses, and re-action 

 polygons and their properties (a new general class of graphical 

 polygons suitable for the comparison of the bending moments and 

 shearing stresses in simple girders and single intersection trusses, 

 due to a moving train of wheel weights), by H. T. Eddy ; on an im- 

 proved method for testing metals, by Charles E. Monroe ; on the 

 effect upon the strength of iron by subjecting it to a pull while hot, 

 Rankine's solution of the problem of turbines, and downward 

 draught device for a furnace, by DeVolson Wood ; on a new high- 

 speed steam-engine indicator, by J. Burkitt Webb ; on errors of 

 approximate calculations of the effect of the inertia of the moving 

 parts of a steam-engine, by D. S. Jacobus ; on the theoretical 

 effect of errors of observation in calorimeter experiments for de- 

 termining the latent heat of steam, and improved arrangement of 

 Siemens's platinum electrical pyrometer, by J. E. Denton ; on the 

 uniformity of planimeter measurements, by T. C. Mendenhall and 

 John Mack ; on mechanical inspection of railway-tracks and results 

 obtained, by P. H. Dudley ; on the theories of the lateral pressure 

 of sand against retaining walls, by Mansfield Merriman ; on 

 national armament, by J. R. Haskell. 



A number of these papers were accompanied by illustrative 



models or drawings, and some by both models and drawings. In 

 some cases only a partial treatment of the subject was given, a 

 complete consideration being reserved for another paper. In this 

 way new lines of thought were suggested, and the authors thus in- 

 dicated their intention of occupying the fields of thought which 

 they thus partially opened up. 



The section united with Section B (Physics) for an hour on 

 Friday to hear two papers by J. Burkitt Webb, — one on a new 

 dynamometer, which was illustrated by a working model ; and the 

 other on the experimental determination of the re-action of a liquid 

 jet. 



On Monday afternoon Sections D and I combined to listen to 

 four papers relating- to different aspects of a plan for a Nicaragua 

 ship-canal. The first of these was on the general subject of 

 isthmian transit, by H. C. Taylor ; the second, on the engineering 

 features of the Nicaragua Canal, by K. E. Peavy ; the third, climatic 

 and sanitary notes on the Nicaragua Canal route, by John F. 

 Bransford ; and the fourth, historical and geographical notes con- 

 cerning the Nicaragua Canal route, by J. W. Miller. The work of 

 the section may be mainly classified under four heads : — 



1. Papers recording actual practical work in new fields ; as, for 

 example, the paper on the mechanical inspection of railway-tracks, 

 which was accompanied by rolls of diagrams taken upon different 

 lines of railway, showing the condition of their tracks, and from 

 \vhich the interesting and valuable results set forth in the paper 

 were obtained. 



2. Papers illustrating new or improved special machines or de- 

 vices for accomphshing difficult ends. The new high-speed steam- 

 engine indicator, by Professor Webb, illustrates this class. A 

 model and drawings of the instrument were shown, by means of 

 which the theory and operation of the indicator were readily under- 

 stood. 



3. Papers based upon laboratory' experiments, like Professor 

 Denton's, on calorimeter experiments for determining the latent 

 heat of steam, in which the results of experiments with two forms 

 of calorimeter were recorded, and made the basis of valuable de- 

 ductions in regard to the theory and operation of the calorimeters 

 compared. 



4. Discussions, suggestions, and criticisms relating to the applica- 

 tion of laws and principles, and to methods of research and com- 

 putation, of which Professor Eddy's paper, on re-action polygons 

 and their properties, is an example. 



The papers were generally fresh and stimulating, and clearly 

 aimed to advance scientific thought and attainments, to secure the 

 practical achievement of valuable work upon a scientific basis, and 

 to perfect theories and harmonize them with actual facts and to 

 secure their easy and correct applications in new fields of scientific 

 work. The sessions of the section must have proved of value to 

 all who followed the work done, and many regret that most of the 

 papers must appear in abstract rather than in full in the Proceed- 

 ings of the association. 



Section E. 



Geography is by title included with geology in Section E of the 

 association ; but geology takes all the attention, and, in the present 

 vigorous condition of geological investigation, geography as a 

 science is almost forgotten. Under geology itself, the work of the 

 International Congress of Geologists and of its American com- 

 mittee received the greatest share of time, as the vice-presidential 

 address of Mr. Gilbert considered the first, and the several reports 

 read by Dr. Frazer introduced the second. There has been appre- 

 hension among some that more might be attempted by the congress 

 in the way of authoritative dictation and majority rulings on mat- 

 ters of opinion than would be justifiable in our rapidly advancing 

 science — or, indeed, in any science. The dangers of such a course 

 were well pointed out by Mr. Gilbert : " The proper function of the 

 congress is the establishment of common means of expressing the 

 facts of geology. It should not meddle with the facts themselves. 

 It may regulate the art of the geologist, but it must not regulate 

 his science. Its proper field of work lies in the determination of 

 questions of technology ; it is a trespasser if it undertakes the deter- 

 mination of questions of science. It may decree terms, but it must 

 not decree opinions. . . . For science it is not merely illogical, it is 



