100 British Associatio7i for the Advancement of Scie?ice. 



dency to combine in that way. A possible explanation is that 

 this is due to the powerful electrical effect which the sharp edges 

 and points of bodies are known to possess : in fact, that electricity 

 is either the cause or the attending consequence of the combina- 

 tion of vapor with a metallic body. Again, if a minute particle 

 of iodine is laid on a steel plate, it liquefies, forming an iodide of 

 iron, and a dew spreads around the central point. Now, if this 

 dew is examined with a good microscope, its globules are seen 

 not to be arranged casually, but in straight lines along the edges 

 of the minute strise or scratches which the microscope detects 

 even on polished surfaces. This is another proof how vapor is 

 attracted by sharp edges, for the sides of those striae are such. In 

 regard to the sensitiveness of his photogenic paper, Mr. T. stated, 

 that it will take an impression from a common argand lamp in 

 one minute, which is visible though weak. In ten minutes the 

 impression is a pretty strong one. In full daylight the effect is 

 nearly instantaneous. 



Mr. Scott Russell brought up the Report by Sir John Robinson 

 and himself, the committee on Waves. Since the last meeting 

 the committee had continued their researches, and had in each 

 department confirmed or corrected the results formerly obtained 

 by them, and had also extended their acquaintance with several 

 interesting phenomena. The first object of their attention was 

 the determination of the nature and laws of certain kinds of 

 waves. Of these, the most important species was that called by 

 Mr. Russell, the Great Solitary Wave, or the Primary Wave of 

 Translation : the second, was the Oscillatory Wave or secondary 

 species. The recent researches, while they had confirmed and 

 extended the observations of preceding years, have in no respect 

 altered the views formerly stated by the committee. The form 

 of the wave is that to which the name hemicycloid has been 

 given ; its velocity is that due to half the depth of the fluid, reck- 

 oned from the top of the wave to the centre of gravity of the sec- 

 tion, where the depth of the channel is not uniform. The mo- 

 tion of the particles, is a motion of permanent translation in the 

 direction of the motion of the wave, through a space equal to 

 double the wave's height ; the particles of the water perfectly at 

 rest before the approach of the wave, are lifted up, translated 

 forwards, and deposited perfectly at rest in their new locations,— 

 the translation taking place equally throughout the whole depth 

 of the fluid. 



