^44 On the Suhmarme Current at the Strait qf‘ Gibraltar^ 
gale of easterly wind, in approaching the rock of Gibraltar, 
When night came on, it became necessary to lay the ship to, 
under a close- reefed main-topsail, to wait for day light and bet- 
ter weather, and this was done as nearly as possible in the mid 
channel. About one o’clock in the morning. Lieutenant Pat- 
ton observed an unusual darkness on the lee beam, and suppo- 
sing it to be land, and the vessel to be in imminent danger, he 
instantly wore the ship, without waiting even to acquaint the 
captain^ Finding it impossible to clear the land by setting 
sails, he saw that there was no chance of saving the ship but by 
trusting to the anchors. One of them was accordingly let go, 
but before it took effect the vessel struck the ground three 
times, but the ship, notwithstanding the very high swell, and 
the breakers within half a cable’s length of the stern, rode fast 
till daybreak, when the weather became more moderate, and the 
vessel was found to have drove in at the back of the rock of 
Gibraltar, by a counter current. 
In consequence of this narrow escape from shipwreck. Lieu- 
tenant Patton was led to study the subject of the currents of the 
Strait of Gibraltar. 
He had ascertained by experience,” says his brother, Cap- 
tain Patton, “ that when two fluids meet in a narrow channel, 
the one being lighter than the other, that which is heaviest will 
run out below, at the same rate exactly that the fluid which is 
lightest runs in above. Of the truth of this, any person may 
satisfy himself by filling two long phials, one with salt water, 
and the other with fresh ; colour one of them with ink, or any 
other substance to distinguish it, and place the mouths of the 
phials close together, holding them horizontally, the salt water, 
which is heaviest, will be seen to run out below, exactly at the 
same rate that the fresh water, which is lightest, runs in above. 
The same law of nature holds with respect to air, which is also a 
fluid ; if, for example, the air in a room is more heated than the 
air in the outside, or next apartment, it will of consequence be- 
come more rarified and lighter ; if the doors be opened between 
them, and a lighted candle be placed on the floor of the passage 
of the door, the flame will blow inward with the cold air run- 
ning in below ; but if the candle is held up near the upper part 
