220 



SCIENCE. 



[N. S. Vol. IX. No. 215. 



by porous materials.' This paper gave the re- 

 sults of experiments on the transmission and re- 

 flection of sound by such materials as flour, 

 sand, sawdust, shot and a few different kinds 

 of cloths. It was stated that when sound waves 

 strike against materials pervious to air they 

 act very much like a pneumatic pressure, and 

 that the amount of sand transmitted throvigh 

 such materials is inversely proportional to the 

 resistance offered by the materials to the pass- 

 age of a direct current of air. The results of 

 the experiments upon the reflection of sound 

 from the same materials showed that those ma- 

 terials that transmitted the greatest amount of 

 sound reflected the least. The paper also 

 contained an account of some experiments in 

 which the sound waves had to pass through 

 some pervious material, such as the curtains 

 upon a wall, and were then reflected back 

 through the same by the impervious wall. 



In the discussion that followed the reading of 

 the paper Professor Hallock suggested the 

 practical application to the improvement of the 

 acoustics of rooms which might result from 

 these investigations, and the futility of the 

 method of string wires in large halls to break 

 up echoes, which had been often advised, but 

 which was disproved by these experiments. 

 Mr. Dudley also spoke of the attempts that 

 had been made to obtain materials absorptive 

 of sound, to deaden the noise in railroad cars. 



The third paper was by Mr. P. H. Dudley, on 

 ' Translative curves of counter balance and 

 crank pins in running locomotives.' It was 

 profusely illustrated by lantern views of loco- 

 motives in the various positions described. 

 These showed the loci of the center of gravity 

 of the counter weights, crank pins and driving 

 axles in running locomotives. Some of the 

 photographs showed the position of the counter 

 weights in the driving wheels of running loco- 

 motives in reference to the stremmatograph 

 under the rail. The counter weights added to 

 the driving wheels to balance the reciprocating 

 parts, crank pins, main and side connecting 

 rods, when the engine is running, besides ro- 

 tating around the axles, move along the rails 

 per revolution a distance equal to the circum- 

 ference of the drivers. The locus of the center 

 of gravity of the counter weights six inches from 



the tread of the tire in a seven feet driving 

 wheel travels above the locus of the driving 

 axle more than three times as far as it does 

 below. The locus of the center of gravity of the 

 crank pin for 24-inch stroke of piston in a driv- 

 ing wheel of 7-feet diameter travels 44 per cent, 

 more above the locus of the driving axle than 

 below it. 



The above cited facts show that the relative 

 velocities of the center of gravity of the counter 

 weights and crank pins are not constant for 

 each portion of a revolution as in the stationary 

 engine, but are unequal and constantly chang- 

 ing. Therefore, the forces generated are un- 

 equal, and perfect counter balance does not 

 obtain in the locomotive. Part of the unbal- 

 anced forces must be absorbed by the locomo- 

 tive itself and part by the permanent way. 

 The upper portion of the driving wheel moves 

 much faster than the lower portion running on 

 and in contact with the rail, in striking con- 

 trast to the uniform velocity of the rim of the 

 fly wheel of a stationary engine. 



Dr. Dudley also showed lantern views of 

 running locomotives, in which the lower spokes 

 of the driving wheels were sharply defined, 

 while the upper ones, running so much faster, 

 were not stopped for the same exposure. 

 Reginald Gordon, 



Secretary. 



THE ACADEMY OF SCIENCE OF ST. LOUIS. 



At the meeting of the Academy of Science of 

 St. Louis of January 23, 1899, a paper by 

 Professor A. S. Hitchcock, entitled ' Studies 

 on Subterranean Organs, Part I, Compositse 

 of the vicinity of Manhattan, Kansas,' dealing 

 with the structure of a number of rootstocks 

 with reference to their environment, was pre- 

 sented in abstract. Mr. C. H. Thompson also 

 spoke of some plants the flowers of which orig- 

 inate endogenously. He mentioned several 

 species of Rkipsalis in which the much reduced 

 leaves grow on triangular or cylindrical very 

 succulent stems, their axillary buds originating 

 deep down in the soft tissue and sometimes 

 having a passage-way extending toward the 

 surface. In two species of Rhipsalis {R. para- 

 doxa and B. floccosa) there is no such passage- 

 way, and the bud, in developing, breaks 



