112 
On Water and Air. 
[February, 
ON WATER AND AIR* 
By John Tyndall, D.C.L., LL.D., F.R.S., 
Professor of Natural Philosophy at the Royal Institution 
of Great Britain. 
Lecture II. 
f OU must be disposed to imagine that water, because it 
is so easily movable or so easily tossed aside by the 
hand in passing through it, would be, like air, very 
compressible, and that you could squeeze it into a smaller 
space. Now this would be a gross error. Notwithstanding 
this wonderful mobility that it possesses, it is almost incom- 
pressible. The first attempt to compress water was made 
in the year 1620, by the illustrious philosopher Bacon. He 
wanted to ascertain whether water was, like air, capable of 
compression, and he operated thus He got a globe of lead 
similar to that which I have here. This was made for me 
by my exceedingly obliging friend, Prof. Abel, of Woolwich. 
This is exactly the first form of Bacon’s experiment when 
he attempted to compress water. He filled the globe of 
lead with water, and he placed it upon an anvil. He then 
took a great sledge-hammer, as I do now, and endeavoured 
to squeeze the globe of lead into a smaller shape ; he beat 
the lead again and again, and tried to compress the water. 
Well, he did compress it to a certain extent ; but he found, 
as he himself in his own quaint language expresses it, that 
the water, impatient of further pressure, finally exuded 
through the lead and covered the surface of the globe like a 
dew. Here, then, we have an instance of the incompressi- 
bility of water as evidenced in Bacon’s first experiment. 
Nearly fifty years afterwards a similar experiment was made 
by a member of that great Academy, the Accademia del 
Cimento, of Florence. They used a silver globe instead of a 
lead globe, and, on account of the Academy having pub- 
lished a description of the experiment, it usually goes by 
the name of the Florentine experiment. But it has been 
* Being a Course of Six Le&ures adapted to a Juvenile Auditory, delivered 
at the Royal Institution of Great Britain, Christmas, 1879. Specially re- 
ported for “ The Journal of Science.’* 
