43 
at small intervals of time, in a safe manner, so as to have 
an explosion engine ; in which, if all the heat of the coal 
could he used in exploding water, rather than in raising 
steam, a surprising economy of fuel should result. 
But as no progress was made in such an engine, I can 
only refer to some old accounts of an explosion in a copper 
foundry, where the great establishment was literally blown 
up, it was said, by a workman simply spitting into a vessel 
of melted copper. The mere amount of steam raised from 
the saliva would evidently have been of no practicable avail 
for either good or evil, even if employed in the best modern 
expansive engine on the thermo-dynamic principles ; but, as 
an explosive, its energy would seem to have been so vast, that 
I must hope for further development of the subject at the 
hands of the able men of science in the Manchester Literary 
and Philosophical Society. 
“On the Destruction of Sound by Fog and the Inertness 
of a Heterogeneous Fluid,” by Professor Osborne Eey- 
NOLDS, M.A. 
1. That sound does not readily penetrate a fog is a matter 
of common observation. The bells and horns of ships are 
not heard so far during a fog as when the air is clear. In a 
London fog the noise of the wheels is much diminished, so 
that they seem to be at a distance when they are really 
close by. On one occasion during the launch of the Great 
Eastern the fog was reported so dense that the workmen 
could neither see nor hear. 
2. It has also been observed that mist in air or steam 
renders them very dull as regards motion. This is observed 
particularly in the pipes and passages in a steam engine. 
Mr. D. K. Clark found in his experiments that it required 
