264 



SCIENCE. 



[N. S. Vol. XXIV. No. 609. 



Y., and a former member of the Isthmian 

 Canal Commission. As the paper has been 

 published in full, and will be found on page 

 71 of the issue of ^cience for July 20, 

 1906, its contents need not be detailed here. 

 Suffice it to say that the recent dread- 

 ful earthquake disaster at San Francisco 

 constitutes the gravest warning in human 

 experience of the advisability of construct- 

 ing this canal in such a way as to give it 

 the greatest degree of immunity from the 

 results of any convulsions of nature, and 

 the stil] more recent earthquake shocks on 

 the isthmus should be sufficient to set even 

 politicians to thinking what would be at 

 least one result of an earthquake to the 

 gates and walls of a lock canal having 85 

 feet of lift. 



In this connection it should be noted that 

 while no efforts have been made to secure 

 authors of papers who were in favor of 

 the sea-level canal, yet all the papers which 

 have been presented before this section 

 in the last few years have logically given 

 most excellent reasons why the canal 

 should be built with the fewest possible 

 locks and of the least lift. Time will de- 

 cide whether the prediction is correct 

 which has been made before this section 

 that the high lock level canal will have to 

 be rebuilt before it has been in use ten 

 years. 



Henry T. Eddy, professor of engineering 

 and mechanics, University of Minnesota, 

 Minneapolis, Minn., presented a paper on 

 'The Theory of the Flexure of the Sym- 

 metrically Loaded Plate, and the Heavy 

 Horizontal Disc of Varying Thickness.' 

 Although the theory of the elastic flexure 

 of the thin flat plate of uniform thickness 

 has been long known to the same degree of 

 approximation as that of the common the- 

 ory of flexure of beams, the theory of the 

 heavy horizontal disc on a vertical axis and 

 of a thickness decreasing from the axis of 

 the rim has, up to the present time, been 



in a somewhat unsatisfactory state from 

 the point of view of the engineer who 

 would design discs like those employed in 

 the Curtis steam turbine. The object of 

 this paper is to make a contribution to this 

 theory, which it is hoped will facilitate 

 both the algebraic and numerical treatment 

 of such units of construction, 



A paper was read and illustrated by 

 Henry S. Jacoby, professor of bridge en- 

 gineering, Cornell University, Ithaca, N. 

 Y., on the 'Applicability of Displacement 

 Diagrams in the Design of the Flanges of 

 Arch Ribs with Solid Webs.' 



The usual method of finding the stresses 

 in the flanges of arch ribs with solid web 

 plates involves the computation of bending 

 moments and axial thrusts at a number of 

 sections due to dead and live loads, and 

 also when there are less than three hinges, 

 for changes of temperature and rib short- 

 ening. The formulas for the determina- 

 tion of the horizontal reactions, while com- 

 paratively simple for ribs with a parabolic 

 axis, are complex for a circular axis, and 

 entirely impracticable for other curves 

 such as three or five centered ovals. The 

 method proposed is to assume the solid web 

 plate to be temporarily replaced by an 

 imaginary inelastic system of open web- 

 bing, the panel points of each chord being 

 located in the centers of gravity of the 

 corresponding flange sections. It allows 

 the horizontal reactions to be found by 

 means of displacement diagrams which ap- 

 ply to any form of arch rib. The method 

 also affords the simplest means of finding 

 the deflections under any loading. 



'Some Notes on the Teaching of the 

 Cyclic Analysis of the Gas Engine' was 

 next presented by Arthur J. Wood, as- 

 sistant professor of experimental engineer- 

 ing, Pennsylvania State College, State Col- 

 lege, Pa. 



As a basis for this study and discussion, 

 the results of tests of a flve-horse-power 



