104 o FT 4S RAY. GF 
concerned; it may be neceflary to make fome obfervations 
upon the nature and properties of fluids in general, as fuch, 
1. No fluid can be at reft unlefs every part of it refpec- 
tively be ated upon by an equal force or preffure in every 
direction, till when its feveral parts will neceflarily recede 
from the greater preffure towards the leffler, nor can an 
equilibrium take place. 
2. If two or more fluids of different natures and denfi- 
ties come together, fuch as quickfilver, water, oil and air, 
which will not mix; they will take their places according 
to their fpecific gravities, the denfeft remaining at the 
bottom. 
3. Ifa veffel be filled with either of thefe fluids, and a 
denfer be admitted into it, the latter will expel, and take 
place of the former. 
4. If an empty cylindrical fpace be furrounded on all 
fides by a fluid, which is excluded by fome refifting fur- 
face terminating that {pace, the fluid will neceflarily, upon 
the fudden removal of the obftacle, immediately flow in 
from every fide towards the center of the void; and as it 
flows inwards the parts next furrounding this fpace will 
thereby be crowded together, and force each other up- 
wards, till at length when clofed, the fluid will by its af- 
cent have formed a column dire&tly over the middle of the 
fpace, to a height proportionable to the united force of the 
converging currents. This muft be the cafe with every 
fluid thus flowing into a vacuum; and in a lefler degree 
when a denfer fluid in a fimilar fituation fupplants ararer: 
And the greater the difference of the denfities of the two 
fluids might be, the more confpicuous would be the effe&. 
This reafoning may be illuftrated, and the conclufions 
exemplified by facts which muft have occurred to the 
obfervation of every one. Do we not obferve when a 
fhower of hail, or rain in large drops, falls upon the fur- 
face of ftagnant water, that the water rifes wherever they 
fall, like fo many little inverted icicles, which again 
inftantly 
