146 
cussion of the air has a tendency to facilitate the conversion - 
of rain-forming material into actual drops of rain, then we 
may well suppose that the violent concussions produced by 
lightning discharges, acting on such enormous and dense 
masses of rain-forming material as are usually collected in 
heavy thunder clouds, are amply sufficient to produce these 
sudden and heavy showers of rain. 
I am aware that the effect of a discharge of ordnance is 
usually supposed to be produced by an upward current of un- 
caused by the heat and the gases evolved during the com- 
bustion of the gunpowder ; but as an hour’s sunshine through 
an opening in the clouds, especially when the sun is at a 
considerable altitude, would produce a much greater effect.in 
heating and increasing the bulk of the air, this cannot be 
received as the true explanation of the mode in which the 
effect of a discharge of heavy artillery is produced. 
Mr. Fairbairn stated that he had been making experi- 
ments on the process of cold rolling, as applied to iron. He 
had tested specimens of cold rolled iron manufactured both 
by Mr. Lauth and Earl Dudley. In the former case, a black 
bar from the rolls broke with 26’ 173 tons per square inch, a 
a similar turned bar with 27T19 tons, and a cold rolled bar 
of the same iron sustained 39'388 tons. The elongations, 
which may be considered as the measure of ductility, were 
•200 and ‘220 per unit of length in the case of the ordinary 
iron, and ’079 in the cold rolled iron. A plate of cold rolled 
iron, from Earl Dudley, sustained no less than 5T3 tons 
per square inch. Endeavours were being made to apply the 
invention to railway bars. 
Mr. Brockbank described the Bessemer process of manu- 
facturing iron and steel, and stated his belief that the 
variously colored flames on the surface of newly run steel 
would afford the means of detecting the presence of metals 
and other bodies by the new method of spectrum analysis. 
