‘ 
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* 100 “British Association for the Advancement of Science. 
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 striz 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 strie 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 isa 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 confirraed 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 
pe and deposited perfectly at rest in their new locations, 
he translation taking place equally throughout the whole ¢ 
of the fluid. 
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